JBL Adapters allow you to match up just about any tip to shaft configuration you can imagine and. JBL adapters are constructed from 303 stainless steel to help resist corrosion. This JBL 8" (20.3 cm) adapter is for all the JBL shafts except the Carbine series. Shaft Adapters add versatility to your arsenal by allowing use of multiple spear tips. The JBL adapter has 6 mm threads and makes a great Save-A-Dive Kit Item.