Works with Rhino-Rack Heavy Duty or Vortex cross bar Made from glass re-enforced nylon All necessary hardware is supplied 6 Spacer Blocks (max height 26mm) 2 x M6 x 45mm Bolts The spacer blocks are used to level a 3 bar roof rack system on a vehicle such as a Ute or pick up that may have rear Ute posts or a canopy rack system. Attached between the Rhino-Rack 2500 leg and either a Rhino-Rack Heavy Duty or Vortex cross bar, this set of spacers will raise the cross bar. These leg height spacers have been designed for use on a support bar, set up for long loads - they are not to be used as a 2 bar system under a load bearing cross bar. Made from glass re-enforced nylon, just like our legs, they are strong and flexible. All necessary hardware is supplied. The maximum height stacking that is recommended by Rhino Rack is 42mm.