diff --git a/lib/grommet.scad b/lib/grommet.scad
new file mode 100644
index 0000000..9477340
--- /dev/null
+++ b/lib/grommet.scad
@@ -0,0 +1,109 @@
+/*
+    This file is part of SBC Case Builder https://github.com/hominoids/SBC_Case_Builder
+    Copyright 2022,2023,2024,2025 Edward A. Kisiel hominoid@cablemi.com
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>
+    Code released under GPLv3: http://www.gnu.org/licenses/gpl.html
+
+    grommet(face, style, od, id, wall, assembly, mask)
+    grommet_clip(style, od, id, height)
+
+*/
+
+
+/*
+           NAME: grommet
+    DESCRIPTION: creates different groumet styles
+           TODO: none
+
+          USAGE: grommet(face, style, od, id, wall, assembly, mask)
+
+                         face = "top","bottom","front","rear","left","right"
+                        style = "sleeve"
+                      size[0] = od outside diameter of grommet body
+                      size[1] = id inside hole diameter of grommet body
+                      size[2] = wall thickness of installation
+                     assembly = false
+                      mask[0] = true enables component mask
+                      mask[1] = mask length
+                      mask[2] = mask setback
+                      mask[3] = mstyle "default"
+*/
+
+
+module grommet(face = "bottom", style = "sleeve", od, id, wall, assembly, mask) {
+
+    height = 4.5+(2*wall);
+    enablemask = mask[0];
+    mlength = height+mask[1];
+    msetback = mask[2];
+    mstyle = mask[3];
+    cut = .25;
+    lip_od = od+4;
+    lip_thick = 2.5;
+
+    adj = .01;
+    $fn = 90;
+
+    rotx = face == "rear" ? 270 : face == "front" || face == "left"  || face == "right" ? 90 : face == "top" ? 180 : 0;
+    roty = 0;
+    rotz = face == "left" ? 90 : face == "right" ? 270 : 0;
+
+    rx = face == "left" ? -lip_thick : face == "right" ? lip_thick : 0;
+    ry = face == "front" ? lip_thick : face == "rear" ? -lip_thick : 0;
+    rz = face == "bottom" ? -lip_thick : face == "top" ? lip_thick : 0;
+
+    translate([rx,ry,rz]) rotate([rotx,roty,rotz]) {
+        if(enablemask == true && mstyle == "default") {
+            if(style == "sleeve") {
+                translate([0, 0, -adj-msetback]) cylinder(d = od+.5, h = mlength);
+            }
+        }
+        if(enablemask == false) {
+            if(style == "sleeve") {
+                difference() {
+                    union() {
+                        cylinder(d=od, h=height);
+                        cylinder(d=lip_od, h=2.5);
+                    }
+                    translate([0,0,-adj]) cylinder(d=id, h=height+(2*adj));
+                    translate([-lip_od/2,-cut/2,-adj]) cube([lip_od+(2*adj),cut,height+(2*adj)]);
+                    translate([0,0,2.5+wall]) grommet_clip(style,od,id,wall);
+                }
+                if(assembly == true) {
+                    translate([0,0,2.5+wall]) grommet_clip(style,od,id,wall);
+                }
+            }
+        }
+    }
+}
+
+module grommet_clip(style,od,id,wall) {
+
+    height = 2.5+wall;
+    lip_od = od+4;
+    adj = .01;
+    $fn = 90;
+
+    if(style == "sleeve") {
+        difference() {
+            cylinder(d=lip_od, h=2.5);
+            difference() {
+                translate([0,0,-adj]) cylinder(d=od, h=wall+2*adj);
+                translate([-lip_od/2,-od/2,-adj]) cube([lip_od+(2*adj),2,height-2]);
+                translate([-lip_od/2,-2+od/2,-adj]) cube([lip_od+(2*adj),2,height-2]);
+            }
+            translate([-lip_od,-(od-6)/2,-adj]) cube([lip_od+(2*adj),od-6,wall+(2*adj)]);
+        }
+    }
+}
diff --git a/lib/panel_clamp.scad b/lib/panel_clamp.scad
index 5c673dd..930b355 100644
--- a/lib/panel_clamp.scad
+++ b/lib/panel_clamp.scad
@@ -38,9 +38,10 @@ module panel_clamp(face, screw, style, dia_x, dia_y, height, mask) {
     rotz = face == "left" ? 90 : face == "right" ? 270 : 0;
 
     if(enablemask == true && mstyle == "default") {
+
     }
     if(enablemask == false) {
-        translate([0,0,0]) rotate([rotx,roty,rotz]) {
+        rotate([rotx,roty,rotz]) {
             difference() {
                 cylinder(d2=dia_x, d1=dia_y, h=height);
                 if(screw == "m2") {
diff --git a/mod/case_rack.scad b/mod/case_rack.scad
index 557dd38..13191c9 100644
--- a/mod/case_rack.scad
+++ b/mod/case_rack.scad
@@ -644,6 +644,22 @@ if(side == "bottom") {
                 }
             }
         }
+        // rear fan openings
+        for(r = [0:len(rack_bay_sbc)-1]) {
+            fan_offset = -75+(75-rear_fan_size)/2;
+            if(rack_bay_rear_fan[r] == true) {
+                translate([-gap-wallthick-1+rack_asm_gap/2+75*(r+1)+fan_offset+8,depth-gap-wallthick-adj,(case_z-rear_fan_size)/2])
+                    rotate([90,0,0]) fan_mask(rear_fan_size, wallthick, "fan_open");
+            }
+        }
+        // rear grommet openings
+        for(r = [0:len(rack_bay_sbc)-1]) {
+            grommet_offset = -75+11;
+            if(rack_bay_rear_conduit[r] == true) {
+                translate([-gap-wallthick-1+rack_asm_gap/2+75*(r+1)+grommet_offset+4,depth-wallthick-gap,13])
+                    grommet("front", "sleeve", 10, 4, wallthick, true, [true,10,0,"default"]);
+            }
+        }
         // subtractive accessories
         if(accessory_name != "none") {
             for (i=[1:11:len(accessory_data[a[0]])-1]) {
diff --git a/sbc_case_builder.json b/sbc_case_builder.json
index 5d55745..c0d0f99 100644
--- a/sbc_case_builder.json
+++ b/sbc_case_builder.json
@@ -10919,7 +10919,7 @@
             "case_offset_bz": "0",
             "case_offset_tz": "0",
             "case_offset_x": "0",
-            "case_offset_y": "40",
+            "case_offset_y": "50",
             "cooling": "default",
             "corner_fillet": "3",
             "edge_fillet": "0",
@@ -11048,50 +11048,49 @@
             "pcb_loc_y": "0",
             "pcb_loc_z": "0",
             "rack_bay1_face": "io_shield",
-            "rack_bay1_rear_conduit": "false",
-            "rack_bay1_rear_fan": "false",
+            "rack_bay1_rear_conduit": "true",
+            "rack_bay1_rear_fan": "true",
             "rack_bay1_rotation": "270",
             "rack_bay1_wall": "true",
             "rack_bay1_xyz_loc": "[13, 0, 0]",
             "rack_bay2_face": "io_shield",
-            "rack_bay2_rear_conduit": "false",
-            "rack_bay2_rear_fan": "false",
+            "rack_bay2_rear_conduit": "true",
+            "rack_bay2_rear_fan": "true",
             "rack_bay2_rotation": "270",
             "rack_bay2_wall": "true",
             "rack_bay2_xyz_loc": "[88, 0, 0]",
             "rack_bay3_face": "io_shield",
-            "rack_bay3_rear_conduit": "false",
-            "rack_bay3_rear_fan": "false",
+            "rack_bay3_rear_conduit": "true",
+            "rack_bay3_rear_fan": "true",
             "rack_bay3_rotation": "270",
             "rack_bay3_wall": "true",
             "rack_bay3_xyz_loc": "[162.5, 0, 0]",
             "rack_bay4_face": "io_shield",
-            "rack_bay4_rear_conduit": "false",
-            "rack_bay4_rear_fan": "false",
+            "rack_bay4_rear_conduit": "true",
+            "rack_bay4_rear_fan": "true",
             "rack_bay4_rotation": "270",
             "rack_bay4_wall": "true",
             "rack_bay4_xyz_loc": "[237.5, 0, 0]",
             "rack_bay5_face": "io_shield",
-            "rack_bay5_rear_conduit": "false",
-            "rack_bay5_rear_fan": "false",
+            "rack_bay5_rear_conduit": "true",
+            "rack_bay5_rear_fan": "true",
             "rack_bay5_rotation": "270",
             "rack_bay5_wall": "true",
             "rack_bay5_xyz_loc": "[313, 0, 0]",
             "rack_bay6_face": "io_shield",
-            "rack_bay6_rear_conduit": "false",
-            "rack_bay6_rear_fan": "false",
+            "rack_bay6_rear_conduit": "true",
+            "rack_bay6_rear_fan": "true",
             "rack_bay6_rotation": "270",
-            "rack_bay6_wall": "false",
             "rack_bay6_xyz_loc": "[385, 0, 0]",
             "rack_size": "1u",
             "rack_width": "19",
             "raise_top": "0",
-            "rear_cooling": "fan_hex",
+            "rear_cooling": "fan_1",
             "rear_dualfan_spacing": "6",
             "rear_fan": "1",
             "rear_fan_center": "false",
             "rear_fan_position": "0",
-            "rear_fan_size": "80",
+            "rear_fan_size": "40",
             "rear_io_shield": "false",
             "sbc_bottom_standoffs": "true",
             "sbc_highlight": "false",
diff --git a/sbc_case_builder.scad b/sbc_case_builder.scad
index 2b48a26..61cc336 100644
--- a/sbc_case_builder.scad
+++ b/sbc_case_builder.scad
@@ -123,7 +123,7 @@ Rack_Bay6 = "empty"; //  ["empty", "c1+", "c2", "c4", "hc4", "xu4", "xu4q", "mc1
 rack_bay6_xyz_loc = [0,0,0]; // [0:.5:450]
 rack_bay6_rotation = 0; // [0:90:270]
 rack_bay6_face = "io_shield"; //["solid","blank","io_shield","vent_hex"]
-rack_bay6_wall = false; // [true,false]
+//rack_bay6_wall = false; // [true,false]
 rack_bay6_rear_fan = false; //[true,false]
 rack_bay6_rear_conduit = false; //[true,false]
 
@@ -538,7 +538,9 @@ rack_bay_sbc = [Rack_Bay1,Rack_Bay2,Rack_Bay3,Rack_Bay4,Rack_Bay5,Rack_Bay6];
 rack_bay_xyz_loc = [rack_bay1_xyz_loc, rack_bay2_xyz_loc, rack_bay3_xyz_loc, rack_bay4_xyz_loc, rack_bay5_xyz_loc, rack_bay6_xyz_loc];
 rack_bay_rotation = [rack_bay1_rotation, rack_bay2_rotation, rack_bay3_rotation, rack_bay4_rotation, rack_bay5_rotation, rack_bay6_rotation];
 rack_bay_face = [rack_bay1_face, rack_bay2_face, rack_bay3_face, rack_bay4_face, rack_bay5_face, rack_bay6_face];
-rack_bay_wall = [rack_bay1_wall, rack_bay2_wall, rack_bay3_wall, rack_bay4_wall, rack_bay5_wall, rack_bay6_wall];
+rack_bay_wall = [rack_bay1_wall, rack_bay2_wall, rack_bay3_wall, rack_bay4_wall, rack_bay5_wall, false];
+rack_bay_rear_fan = [rack_bay1_rear_fan, rack_bay2_rear_fan, rack_bay3_rear_fan, rack_bay4_rear_fan, rack_bay5_rear_fan, rack_bay6_rear_fan];
+rack_bay_rear_conduit = [rack_bay1_rear_conduit, rack_bay2_rear_conduit, rack_bay3_rear_conduit, rack_bay4_rear_conduit, rack_bay5_rear_conduit, rack_bay6_rear_conduit];
 
 adj = .01;
 $fn=90;
@@ -1112,6 +1114,23 @@ if (view == "model") {
                     }
                 }
             }        
+            // rear fan covers
+            for(r = [0:len(rack_bay_sbc)-1]) {
+                fan_offset = -75+(75-rear_fan_size)/2;
+                if(rack_bay_rear_fan[r] == true) {
+                    translate([-gap-wallthick-1+.125+75*(r+1)+fan_offset+8,
+                        depth-gap,(case_z-rear_fan_size)/2])
+                            rotate([90,0,0]) fan_cover(rear_fan_size, wallthick, rear_cooling);
+                }
+            }
+            // rear grommets
+            for(r = [0:len(rack_bay_sbc)-1]) {
+                grommet_offset = -75+11;
+                if(rack_bay_rear_conduit[r] == true) {
+                    translate([-gap-wallthick-1+.125+75*(r+1)+grommet_offset+4,depth-wallthick-gap,13])
+                        color("lightgrey") grommet("front", "sleeve", 10, 4, wallthick, true, [false,10,0,"default"]);
+                }
+            }
             if(sbc_off == false) {
                 for(i = [0:len(rack_bay_sbc)-1]) {
                     s = search([rack_bay_sbc[i]],sbc_data);
diff --git a/sbc_case_builder_library.scad b/sbc_case_builder_library.scad
index 484aa8f..e241e2d 100644
--- a/sbc_case_builder_library.scad
+++ b/sbc_case_builder_library.scad
@@ -45,6 +45,7 @@ include <./lib/dsub.scad>;
 include <./lib/fans.scad>;
 include <./lib/fastener.scad>;
 include <./lib/feet.scad>;
+include <./lib/grommet.scad>;
 include <./lib/hd.scad>;
 include <./lib/holder.scad>;
 include <./lib/keyhole.scad>;