Holman Pro II Heavy Duty Leg Extensions - Service Bodies - Black Model 31520Holman Pro II Heavy Duty Leg Extensions Service Bodies Black Model 31520 Leg extension kit for Holman Service Body Racks. It provides a 9 height increase and replaces the 3 extension legs that come with the kit. 31520 can be used to fit tall cabs such as the Chevy 5500 or to provide clearance for specialty equipment.