The Dewey Rod Guide is designed without a chamber sealing o-ring due to limited chamber space and the need for large brush clearance.
It features a front brass bushing that centers the guide in the barrel extension and a large o-ring that locks into the bolt opening to minimize movement during cleaning.
Constructed from Delrin, Brass, and Anodized Aluminum, it is compatible with J. Dewey Cleaning Rods and is specifically made for AR-15/M16 rifles chambered in .223/5.56mm and .204 Ruger.