CMI J racks are 15" (38.1 cm) long, which provides you more space to vary the friction. This feature will be appreciated when doing long rappels. Six (6) 1" (2.54 cm) stainless steel open back bars and a top hyperbar for easy tieoffs. All fixed on a 3/8" (10 mm) stainless steel frame. Will last a lifetime. Use the straight frame on harnesses with a vertical connection point, use twisted frame on harnesses with a horizontal connection point. Accepts ropes from 3/8" (10 mm) to 3/4" (19 mm). Works with doubled ropes too! Both must be same diameter. Weight 30 oz.(840 g). Made in the U.S.A.