Stainless steel weight system. Applies above the BCD's backplate* thanks to the 4 supplied pins, without using any tool. Available versions: 1.9Kg (3mm), 2.2Kg (only for SWAT model) and 2.9Kg 
 
Compatible with Piastra Inox.
*Compatibility is NOT ensured for Backplates other than SCUBA ONE's