The powerblock u90 stage 3 add on kit requires u90 stage 1 2 and replaces 34 pairs of dumbbells or 1783kg 39308lbs of free weights it expands the u 90 up to 57kg 1256lbs per hand and is supplied with 2 additional weight plates and a taller handle set for use with additional weight plates additionally it is part of the urethane series and is shipped in two boxes