Set comprises 2 x SDH4 Handles & 3 boxes of 4 5Kg & 1 box of 4 3.75kg pro Style discs. Pro-Style Dumbbells are supplied un-assembled and require an 8mm Allen key to assemble (code CNDBAK). A big benefit of the pro-style dumbbells is that if a weight plate or handle does manage to get damaged, then they can be easily replaced and this saves you from having to buy a whole new dumbbell.