(Pkg 24) 37mm White Plastic Ping Pong Balls. Amateur Ping Pong Balls Perfectly suitable for all your non-professional ping-pong-ball applications. These guys are white-ish, with a visible seam, and are 37mm in dia, as opposed to the standard 40mm or the former standard 38mm professional ping-pong balls. Priced so you can buy enough to do any number of clever things with them.