This little delrin plug is used to fix the inter stage pressure on an Apeks DS4 first stage and the Wells Marine- FS819 first stage. It will stop the regulator from compensating the I.P with depth and keep it to where you set it.
This is for use with KISS type O2 injection using constant mass flow
DO NOT BUY THIS UNLESS YOU KNOW WHAT IT IS AND HOW TO USE IT....USING THIS ON OPEN CIRCUIT EQUIPMENT COULD BE VERY DANGEROUS