Area 419 Zero Locking Die Ring Multi-Packs include multiple rings and a die wrench. Finish on all multi-packs will be black nitride. Wrenches are aluminum, so the finish is a black hardcoat anodize. Total thickness of rings is .500a ^2 and outside diameter is 1.685a ^2. FeaturesLARGE DIAMETER - more surface contact with the turret head means the ring will align with the press and force the die straight, instead of grabbing onto the die and aligning as it may.MORE THREAD ENGAGEMENT - the rings feature .350a ^2 of thread engagement, which is 15-25% more than common die lock rings. This results in roughly a full thread of additional engagement, increasing the ability of the ring to square the die to the press.INTERNAL WRENCH ENGAGEMENT - with traditional rings, there is a flat or knurling on the outside, which requires you to get a wrench around the outside to tighten. On a multi-die head this requires you to get tools between dies and fight with the location...