diff --git a/follow_focus.py b/follow_focus.py
index 5f6932f..e919fa9 100644
--- a/follow_focus.py
+++ b/follow_focus.py
@@ -96,7 +96,8 @@ lid = lid.faces('>Z[0]').workplane().circle(5/2).cutThruAll()
 
 gear_gap=0.2
 base = base.faces('<Z[1]').workplane().center(21,20.15).circle(25).cutBlind(-gear_thinkness-gear_gap)
-base = base.faces('<Z[2]').workplane().circle(11/2).extrude(-lid_thicknesss+wall_width)
+t=11/2
+base = base.faces('<Z[2]').workplane().hLine(t, forConstruction=True).threePointArc((-t,-t/2),(0,t)).polarLine(t, -slant_degree).close().extrude(-lid_thicknesss+wall_width)
 gear_offset=0.5
 base = base.faces('<Z[2]').workplane().circle(large_gear_diameter/2-gear_offset).extrude(gear_thinkness/2)
 base = base.faces('<Z[2]').workplane().circle(2).cutBlind(-part_thinkness/2+wall_width)