From Colorado Karting Tour:
“As of May 01, 2019, all competitors at Colorado Karting Tour events should be advised that transponders for all divisions will be required to be mounted to the rear face of the seat per CIK / FIA positioning, at a height of 25cm + / – 5 cm. Important note: there will be no exceptions for compliance with this regarding placement of ballast, and there are no other acceptable mounting locations at this time. Please re-locate your transponders before Round 02 of 2019.”