Two timing pulley options for common belt standards are included in this listing. - 1 pc 5M Type 30T timing pulley - Teeth: 30 - Pitch: 5 mm - Inner bore options: 6/6.35/8/10/12/12.7/14/15/16/17/20/22/24 mm - Purpose: for 5M timing belt drives, offering flexible shaft compatibility with a single pulley - 28 mm HTD timing pulley for belt width 20 mm - Profile: HTD 16/21 - Outer diameter: 28 mm - Belt width compatibility: 20 mm Use scenarios - Upgrading or assembling a compact 3D printer axis drive or extruder feed system - Building a small CNC gantry or robotics drive where a reliable 5M or HTD belt is used - Implementing a precise linear actuator or automated conveyor with standard belt widths Key benefits - Wide bore compatibility enables easy shaft matching across multiple installations - Supports two common belt profiles (5M 30T and HTD 16/21) for versatile applications - 30-tooth design provides stable, predictable drive with standard pulleys - Compact 28 mm variant suits tight spaces while handling a 20 mm belt width This description maintains the original specifications and functions: a 1 piece 5M Type 30T pulley with multiple inner bore options and 30 teeth, plus a 28 mm HTD 16/21 pulley for 20 mm belt width.