Kreitler Alloy Roller Drums with alloy end caps are the longest lasting and are compatible with all accessories.Drums are sold in 3 sizes and come with corresponding roller beltRoller frame to be purchased separatelyKiller Headwind compatibleAlloy Drums use CNC machined alloy end capsSmaller diameters provide more resistanceAlloy end caps are the longest lasting, compatible with all accessories and give the truest feel of being on the road