Compatible ink cartridge for the following Pyramid time clock models: 3000, 3000HD, 3500, 3500SS, 3500HD, 3700, 3700HD, 4000, 4000HD. Black ink, long life, premium quality, direct replacement for Pyramid 4000R. NOT compatible with Allied Time AT-3500. NOT compatible with the following Pyramid models: 3550SS, 3600SS, 4000pro, 5000