Bell introduced the SRV friction-lock system as a rolling production change in 2005-06 on the SA2005 Dominator, Vortex, M3 / M3 Xtra, GTX, M4 Pro, and BR-1 helmets.
Some of the early SA05 helmets have the original Kam-Lok detent system, but later SA05 versions of these models have the SRV system. The SRV shield has a smooth curved slot in front of the pivot and takes a different shield.
Note that Bell has now stopped production of new Kam-Lok shields. The newest helmets originally equipped with Kam-Lock sheilds are now at the end of their life and should be retired. A Bell Kam-Lok to SRV Conversion Kit is available to allow those helmets to accept SRV shields.