diff --git a/common.scad b/common.scad
index 3442c5f..dd20aa3 100644
--- a/common.scad
+++ b/common.scad
@@ -24,6 +24,9 @@ module tube(o = 1, i = 0, h = 1, center = false, $fn = 12) {
 module m3_nut (H = 5) {
   cylinder(r=R(6.6), h=H, center=true, $fn=6);
 }
+module m4_nut (H = 3.1) {
+  cylinder(r = R(8.1), h = H, center = true, $fn = 6);
+}
 
 module rounded_cube (cube_arr = [1, 1, 1], d = 0, center = false) {
   off_x = 0;