The included retaining ring holds a 1.875" x 1.25" smoke graiin. The top of the bulkhead has a 3/8-16 threaded hole for an eyebolt.
These bulkheads are capable of "experimental" (but proven) head-end ignition with a modified smoke grain. Contact us for more information.
The liner shoulder incorporates an o-ring acting similarly to a seal disk found in other brands. This feature is strictly for use with convolute phenolic liners. Spiral wound liners must not use this o-ring as damage to the motor may occur.