Atlas MFC Milling Machine 24 tooth bevel gear MF-3A 1/2" bore and 30 tooth gear MF-18B These fine Nylon gear has improved design for better durability and performance compare to OEM and superior to other replacements US made out of Nylon - tough and flexible plastic Nylon naturally slippery, no lubrication required! Runs quieter and smoother Only Nylons should be used for gears where a slippery surface is desired. All other materials (PLA, ABS, PET, etc.) will grind creating a plastic dust and eventually fail! For details, please review all pictures MF3A Tooth count 24 DP 24 O.D. : 1.083" (27.5mm) Bevel Gear face width: "3/8" (9.52mm) Straight gear face width 0.771 Center bore: 1/2" (12.7mm) Radial Pin hole 1/8" MF-18B Tooth count 30 DP 24 O.D.: 1.33 Gear Face width: 0.32" Center Bore 0.3125 Square