Abstract: A caster structure for cases including a coupling frame and a plurality of rollers. The coupling frame is comprised of a curved plate and two protective covers extending from the lateral edges of the bottom side of the plate such that they define a clearance therebetween. The rollers are pivotally mounted on the protective covers in the clearance. The outer circumferences of every two adjacent rollers form a level line and may come into contact with the ground surface simultaneously to facilitate pulling and provide a steadier movement.

Abstract: A retractable handle positioning structure including two sleeves connected between a top mounting frame and a bottom mounting frame, two inner tubes joined by a hand grip and moved in and out of the sleeves, a control bar mounted in the top mounting frame and turned on its own axis, two longitudinal racks respectively mounted on the inner tubes inside the sleeves, and two locating blocks mounted around two opposite ends of the control bar and moved between the locking position in which the locating blocks are meshed with the racks to hold the inner tubes in position, and the unlocking position in which the locating blocks are disengaged from the racks for permitting the inner tubes to be moved relative to the sleeves.