Trackball Assembly 2-1/4" - 56-5500-1: Choose your color. Durable black polycarbonate plastic material. 2-1/4" diameter ball. Standard AMOA harness included. Mounting hardware sold separately. Can be used as a heavy duty alternative to a mouse for interactive displays when used in conjunction with trackball interface kit. Translucent ball optional. Part Number: 56-5500-1. Your choice of color. Item is a component in the following:Namco Capsule Factory. Taito: Birdie King, Birdie King 2. Team Play: Centipede