ROLLER STYLES: REGULAR AND GUIDED The plastic inserts can alternatively be replaced with a guided version of the rollers. With the guided version, the cylinder tapers towards the centre. This means that the barbell is positioned automatically in the centre and is relatively fixed by its own weight, so the movement of the barbell to the front or back is being reduced. The default version of the Roller J-Hooks are the standard flat roller inserts. The guided version can be added from the menu. SPECS Material Roller J-Hooks: black powder coated steel, UHWM protective plastic inserts Roller material: hard rubber Exchangeable roller style - regular to guided Sizing: 60mm or 75mm Replaceable plastic inserts The j-hooks as well as the separate rollers are sold in pairs Please note: The J-Hooks are delivered with the standard flat roller variant, the guided roller elements need to be ordered in addition.