The Z33 Standard Body TailCap end Lanyard Ring is designed to rotate freely so that your lanyard does not end up tangled.
The Z12 Standard Body Bezel end Lanyard Ring is designed to be held tight between the body and the Bezel (or TurboHead Adapter collar).
Sometimes especially for longer SureFires such as the 9PT, 7ZT, 12PM etc, a Z12 Bezel Lanyard Ring will help protect the Bezel when you let go of the SureFire and let it dangle from your wrist.
I have a Lanyard on all my larger SureFires.
Especially my Classic 12PMT which is not shock isolated.
I've never had any problems with my SureFire Lanyards or lanyard rings.
Some say they aren't stealthy [not totally quiet] enough. From my perspective that's not an issue because I don't sneak up on people that often. The Classic 6Z has been in use for years and years and in the four years I've been researching SureFires, it's not been an issue. In fact, Lanyards are generally accepted as good and important.
You don't have to use a Lanyard, it is one of several options including the Z21 TailCap [with a Lanyard attach ring instead of a pressure switch (no momentary switching) which I'm using on a 9PT at the moment]
I've sorted my G2-OD out with a Z33 TailCap Lanyard Ring and Z28 OD Lanyard. When I'm out and about in the dark, I often have a G2 hanging from my wrist whilst in the hand, I'm holding a longer range SureFire such as the M4 or 9AN+KT3 (both of mine are fitted with TailCap Lanyards. The 9AN TailCap Lanyard Ring is the Z12.)
Al