The Redrock Micro microLensGear Kit Blue includes four different gears, namely A, B, C, and D. These industry-standard film pitches are attached with the still photography lenses to be used with microFollowFocus. The fastening screws in the Redrock Micro microLensGear Kit Blue helps in fitting the lens securely.A single thumb screw helps in attaching and tightening the microLensGear quicklyThe Redrock Micro 35mm DSLR LensGear Kit is designed exclusively to fit various sizes of lensThese gears in the Redrock Micro microLensGear Kit Blue have larger diameter for accurate focus and get better control over focusThe film pitches are made from proprietary lubricated nylon to render durable performanceThe external focusing lenses can be geared to these wider gears and used with the follow focusCircumference Size: Size A - 180mm - 220mm, Size B - 211mm - 250mm, Size C - 241mm – 280mm, Size D - 280mm-320mm