TBR-130 Tribar arms are support arms that hook into a CMP-485 Super Clamp (sold separately). When used together, Tribar arms and a Super Clamp form one APEX tier to be used on an APEX AX-48 Pro keyboard stand. Total load capacity is not to exceed 250 lbs. and only two tiers are encouraged. The TBR-130 Tribar arms are 13" in depth and are intended to support mid- to small-sized keyboards. Also available are TBR-180 18" Tribar arms for use with deeper, larger keyboards, synths, and workstations.