Kwikee's upgrade kits include the IMGL (Integrate-Motor-Gearbox-Linkage), control unit, and door switch. All are designed to update your original step motors on all step models prior to 2006. Kits are available in A, B or C linkage. ; Upgrade your motor and control for steps with this complete kit. ; Replacement kit for 28,31,37,39 series; IMGL/9510 control. ; Best for steps made 1999 through 2005.