The Sport 9.0 is a component dumbbell system, offering the user the opportunity to expand the set, as strength training needs change. With a different inner core handle to the 2.4 and 5.0 models, Sport 9.0 Stage I Set has two 1kg adder weights that slot inside the handle for micro-incremental training in steps of 1kg per hand to fine-tune workouts for maximum versatility. At its Stage I point, the Sport 9.0 set is equal to and replaces the need for, 16 pairs of traditional fixed-weight dumbbells. Weight range is 1kg-22.5kg with increments per hand. Stage II When you purchase the additional Stage II Kit, the Sport 9.0 expands to accommodate an extra 12 pairs of dumbbells, giving the following additional weight increments 25, 26, 27, 29.5, 30.5, 32, 34, 35, 36, 38.5, 40 & 41Kg.