Two cargo bed lengths were used; one for the seven-foot long-bed model, which appeared first in 1986, and a second, shorter version for the six-foot cargo bed, which debuted for the 1987 model year. Unlike other pickups of the time that used C-channel frames, the Comanche's frame design (called a "Uniframe" by Jeep) under the cargo bed was fully boxed, with a large X structure centered over the rear axle. For strength, the rails were over eight inches deep (top to bottom), much deeper than conventional midsize truck frames (1983 Jeep J-10 full-size truck frame is 6.75 inches at the deepest point). This structure was pioneered by AMC for the 1971 "Cowboy" compact pickup prototype.