Customized version of http://www.thingiverse.com/thing:41274

Fits this potentiometer:
www.robotshop.com/productinfo.aspx?pc=RB-Ite-06

Created with Customizer! http://www.thingiverse.com/apps/customizer/run?thing_id=41274

Using the following options:

16_top_edge_smoothing_radius = 3
pokey_outey = [pokey_outey_value, pokey_outey_value,0]
41_height_of_cylinder_indentations = 15
33_sphere_indentation_location_y = 0.0
43_position_of_cylinder_y = 0
13_set_screw_height = 4
02_knob_diameter_bottom = 20
23_arrow_shaft_scale = 1.5
06_shaft_height = 7
11_set_screw_diameter = 3
38_smoothness_of_cylinder_indentations = 50
29_sphere_number_of_indentations = 12
14_quality_of_set_screw = 20
01_knob_diameter_top = 20
09_shaft_hole_flat_size = 5.0
26_arrow_location_y = 1.0
arrow_indicator_translate = [25_arrow_location_x,26_arrow_location_y,27_arrow_location_z]
translation_of_cylinder_indentations = [42_position_of_cylinder_x,43_position_of_cylinder_y,44_position_of_cylinder_z]
37_number_of_cylinder_indentations = 7
15_top_edge_smoothing = true
42_position_of_cylinder_x = -2
10_set_screw = true
07_shaft_smoothness = 20
40_diameter_of_bottom_of_the_cylinder = 7
34_sphere_indentation_location_z = 15.0
28_indentations_sphere = false
39_diameter_of_top_of_the_cylinder = 4
22_arrow_head_scale = 2.0
05_shaft_diameter = 6.2
45_cylinder_starting_rotation = 0
03_knob_height = 16
25_arrow_location_x = 0.0
30_sphere_quality_of_indentations = 40
18_pointy_external_indicator = true
08_shaft_hole_is_flatted = false
translation_of_sphere_indentations = [32_sphere_indentation_location_x,33_sphere_indentation_location_y,34_sphere_indentation_location_z]
31_size_of_sphere_indentations = 4
24_arrow_indicator_scale = 1.3
32_sphere_indentation_location_x = 10.0
36_indentations_cylinder = true
20_pointy_external_indicator_pokey_outey_ness = 1.0
35_sphere_indentation_starting_rotation = 0
04_knob_smoothness = 25
21_top_of_knob_arrow_indicator = true
12_set_screw_depth = 9
44_position_of_cylinder_z = -5
27_arrow_location_z = 16.0
17_top_edge_smoothing_smoothness = 20
19_pointy_external_indicator_height = 3