diff --git a/mini-tube.scad b/mini-tube.scad
index 9b186c5..268dfe4 100644
--- a/mini-tube.scad
+++ b/mini-tube.scad
@@ -1,15 +1,20 @@
 $fa = $preview ? 5 : 1;
 $fs = $preview ? 0.1 : 0.01;
 
-volume_ml = 5;
+volume_ml = 5; // .1
 cross_section_mm2 = 100;
-marks = [[1, 30], [.2, 15]];
+marks_small_ml = .2; // .1
+marks_medium_ml = 0; // .1
+marks_large_ml = 1; // .1
 
 extra_height_mm = 5;
 wall_thickness_mm = 0.8;
 mark_depth_mm = 0.3;
 mark_width_mm = 0.4;
 
+marks_pre = [[marks_large_ml, 30], [marks_medium_ml, 20], [marks_small_ml, 15]];
+marks = [for (m = marks_pre) if (m[0] > 0) m];
+
 bottom_thickness_mm = wall_thickness_mm;
 
 cross_section_cm2 = cross_section_mm2 / 100;