specially compounded rubber. The sizes range from 4 ½” to 20”.
Three core designs are used for these plugs:
- A solidcore is used for casing sizes from 4 ½” to 6 5/8”.
- A pinwheeldesign is employed for casing sizes 7” through 13 3/8”.
- An octagonal core design with solid wooden hub and eight spokes is used for the 16” to 20” casing.
