The powerblock u33 stage 2 add on kit has a compact and innovative design and requires the powerblock u33 stage 1 adjustable dumbbells it increases the weight range of the u 33 stage from 1 to 15kg 2 33lbs per hand and keeps weight close to the hand to improve control and balance in addition the kit replaces 25 pairs of dumbbells or 393kgs 8664lbs of free weights