Customized version of http://www.thingiverse.com/thing:57768

Created with Customizer! http://www.thingiverse.com/apps/customizer/run?thing_id=57768

Using the following options:

rings = 5
sidestep = 12
inner_max = .7
wiggle_room = 20
max_thick = 3
ring_max = 55
ring_min = 10
min_thick = .4