Set comprises 2 x SDH4 Handles & 4 boxes of 4 5Kg 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.