This is a parametric set of lens-gears for a follow focus. Compatible with industry standard follow focus systems. (Yes, these things cost an arm and a leg in shops.) pitch: 0.8 #tooth: 97 all gears have the same outer but different inner diameters. (You you need not adjust your follow focus when switching lenses.) All gears have their nominal inner diameter labeled onto them in 3d letters. 60mm = 56-60mm 62mm = 59-62mm 65mm = 62-65mm 68mm = 64-70mm 70mm = 67-70mm example lens-sizes for a few DSLR lenses: Name ....................... lens gear size (filter size) Panasonic 14-42 ............ 60mm Canon FD 50mm f1.2 (nicht L) 62mm (52mm) Canon FD 50mm f1.2L ........ 65mm (55mm) Canon FD 35-70 f3.5-4.5 .... 62,5mm (52mm) Sun FD 135mm f2.5 .......... 66,5mm (58mm) Tamron FD 28mm f2.5 ........ 60mm (67mm) Tamron SP 28-80mm f3.5-4.2 . 68mm (67mm) Tamron SP 60-300mm f3.8-5.4 68mm (62mm) RMC Tokina 70-210mm f3.5 ... 70mm (62mm) Blog post: marcuswolschon.blogspot.com/2011/07/parametric-lens-gear-set.html Photos: picasaweb.google.com/Marcus.Wolschon/201105_201106_geared_follow_focus?feat=directlink Shapeways shapeways.com/shops/marcuswolschon (for the few people here without a 3d printer) License is CC-BY-NC-SA So you may make one yourself and improve the design but not sell the design or made parts and always give attribution.