If you want to put a tracer unit on the KWA KRISS Vector GBB, you can use this Hornbill Products KRISS Outer Shell for Star Airsoft Tracer Unit (Power Up Version) which is available right now at RSOV.com. This allows you to have an adapter that can fit the tracer unit to your KRISS Vector GBB. The Star Airsoft Tracer Unit will have to be purchased separately.