CycleOps Climbing Riser Block For a stable, worry-free ride with any rear wheel-mounted trainer. Unique 3-level design lets you select the level of difficulty. Stack two blocks to simulate climbing workouts. Stackable riser block for rear-mounted cycling trainers Unique 3-level design lets you select ideal training height Stacks with 2nd block to simulate climbing workouts Supports up to 12 adjustment levels with 2nd block Virtually indestructible injection-molded construction