The RAP-B-379U-M81208 consists of a 1" diameter rubber ball, connected to a M8-1.25 X 8MM male threaded post.
Metric Thread Diameter and Pitch Option:
M8-1.25 X 8MM
High Strength Composite & Steel
B Size 1" Rubber Ball
The "U" in the part number reflects product packaged in poly bag.