Black Box Explains...Category 3 and 4
Category 3 is the performance level for voice and data transmission up to 16 MHz or 10 Mbps, such as 4-Mbps Token Ring and 10BASE-T.
Category 4 is the performance level for voice and data transmission up to 20 MHz or 16 Mbps, such as 4-/16-Mbps UTP.
Both offer solid performance, and Black Box guarantees their reliability. But if you think you may be upgrading your network within the next few years, consider Category 5 cable. It offers more speed and versatility than Category 3 or 4 at a minimal cost difference.