USBC;
Page 85 Section 2 - Bowling balls paragraph b=5 under, Other Requirements
Read: Designs may be embedded in a ball as guides, or observation, or identification purposes, provided the designs are flush with the outer surface of the ball. There shall be no interior voids and the plugs or designs must be of the same material simular to, although not exactly the same as, the original material out of wich the ball was made:and shall otherwise comply with all bowling ball specifications.:USBC