diff --git a/pressfit_catears.scad b/pressfit_catears.scad
index 7697690..c452da1 100644
--- a/pressfit_catears.scad
+++ b/pressfit_catears.scad
@@ -1,3 +1,5 @@
+/* use manifold backend, CGAL can't hanlde this */
+
 include <globals.scad>;
 
 use <catear_headband.scad>;
@@ -10,7 +12,7 @@ EAR_STRETCH_FACTOR = 1.2;
 
 difference() {
 translate([20*pow(0.99, SIZE/2*EAR_SCALE-1-THICKNESS), 0, -THICKNESS/2])
-union() for (i=[0:SIZE/2*EAR_SCALE-1]) {
+union() for (i=[0:1/EAR_STRETCH_FACTOR:SIZE/2*EAR_SCALE-1]) {
   j=pow(0.99, i);
   chamfer_ = floor(abs(2*i/(SIZE/2*EAR_SCALE-1)-1));
   translate([-j*20, 0, 0])
@@ -29,4 +31,4 @@ union() for (i=[0:SIZE/2*EAR_SCALE-1]) {
 }
 translate([0, 0, -THICKNESS]) cube([100, 100, THICKNESS], center=true);
 scale([1, 1, 2]) inserticle();
-}
\ No newline at end of file
+}