138-SR & 138-AR SERIES SPECIFICATIONS:Rollers: 1-3/8", 18 Ga. Galv./Alum., Axles: 1/4" Round, Spring Loaded, Frame: 2-1/2" x 1" x 1", 12 Ga. Galv. or 1/8" Alum. Formed Channel, 5 Cross Braces, Hook and Bolt Couplers, Standard, Roller Cap. - Steel: 50 Lbs., Alum.: 40 Lbs. 10' Frame Capacity - Steel: 50Lbs/Ft, Alum: 30Lbs/Ft, 5' Frame Capacity - Steel: 200Lbs/Ft, Alum: 100Lbs/Ft