The ServoCity Intake Roller Wheel (8mm REX, 12mm Diameter, 16mm Width, 30A Durometer) - 8pk is designed for creating compact intake systems. These rollers, made from silicone rubber, provide a super grippy surface and fit over an 8mm REX shaft, covering a total of 128mm in length. Each roller weighs 1.7 grams and features a 30A durometer for optimal performance.