DIMENSIONS AND COMPATIBILITY SMALL SIZE (outer diameter of head tube less than 54mm) The outer diameter of the head tube must be at least 54mmWe recommend the use of frames with head tubes with a semi-integrated headset (ZS) on the top section, to avoid any compatibility problems with the G1 rotor and various gyro tabs. This avoids any compatibility problems with the G1 rotor and the various gyro tabs. If your frame does not use a semi-integrated headset (ZS) on the top section, you can use gyro tabs that align with the bottom of the small (69mm) version of the G1 gyro. However, the gyro tabs are not included and will have to be adapted to align with the width of the lower part of the gyro. The fork steerer tube must be at least 20mm longer LARGE (head tube outer diameter greater than 54mm)The head tube outer diameter must be greater than 54mmWe recommend using frames with head tubes with a semi-integrated headset (ZS) on the upper part. This avoids any compatibility problems with the G1 rotor and the various gyro tabs. If your frame does not use a semi-integrated headset (ZS) on the top section, you can use gyro tabs that align with the bottom of the G1 gyro in the small version (74mm). However, the gyro tabs are not included and will have to be adapted to align with the width of the lower part of the gyro. The best way to measure is to use a caliper to measure.the pivot of your fork must have at least 20mm extra length Before ordering the rotor:Be sure to watch the rotor installation video in its entirety (available below)Have a 20mm spacer available (not supplied with 20mm), this will allow the rotor to work properly.check the pivot of your fork must have at least 20mm extra length.