KMDSI recently changed the stepped ring (560-078) and split ring (540-105) for all currently shipping Kirby Morgan® helmets, models 17C, 27, 37, and 57. This announcement was made in Product Bulletin #16 of 2005, which all dealers received a short time ago.
This change in the design of the stepped ring and split ring has also prompted a slight modification to the dimensions of the front yoke hinge, which is exclusive to the SuperLite®-17C.
If a customer orders a replacement stepped ring (new), and they own a 17C Helmet made prior to November 2005, when they reassemble their 17C neck ring assembly (505-101) they will find that their original front yoke hinge, 550-216, will not fit onto the new stepped ring. Therefore, these customers will need to order the new front yoke hinge (no part number change, 550-216) when upgrading to the new stepped ring, 560-078.
Note: The new 550-216 17C front yoke hinge will retrofit the original style 560-078 stepped rings. The new split rings, (no part number change: 540-105, ref bulletin #16 of 2005) have no affect on the fit of any components of the 505-101 SuperLite®-17C neck ring assembly.
The front yoke hinge on the SuperLite®-17C must be the latest version to work with the new stepped ring.