Customized version of https://www.thingiverse.com/thing:16627

Created with Customizer! https://www.thingiverse.com/apps/customizer/run?thing_id=16627

Using the following options:

teeth = 21
profile = 6
motor_shaft = 3.175
m3_dia = 3.2
m3_nut_hex = 1
m3_nut_flats = 5.7
m3_nut_depth = 2.7
retainer = 0
retainer_ht = 1.5
idler = 0
idler_ht = 1.5
pulley_t_ht = 12
pulley_b_ht = 8
pulley_b_dia = 20
no_of_nuts = 1
nut_angle = 90
nut_shaft_distance = 1.2
additional_tooth_width = 0.2
additional_tooth_depth = 0