4-PACK TRACKBALL SET - High quality multi-pack trackball set in red, purple, pink, and lavender for your trackball mouse; Switch up the trackball color to accent your desk setup; The perfect gift for trackball enthusiasts REPLACEMENT TRACKBALL - Designed for any trackball mice using 1.34 (34mm) trackball size; Such as from Perixx: PERIMICE-517/717/520/720, Logitech: MX Ergo, M570, Cordless, Kensington: TrackMan Wheel (not include Trackman Marble), Elecom: M-XT3DRBK (EX-6), M-DT2URBK, EX-G/DEFT Sanwa: MA-WTB43BK SMOOTH SURFACE - The surface is treated with a special coating to provide a precise and smooth tracking performance HOW TO REMOVE THE TRACKBALL - The trackball from PERIMICE-517/717 can be easily removed from the bottom hole of the mouse, using the tip of your finger INSIDE THE BOX - One trackball from each color (Red, Purple, Pink, and Lavender)