This 4 pin CB microphone is the model that comes with the PRO505XL, and is the factory replacement for that CB radio. This microphone will also work with any radio wired 4 pin Uniden, including the following models: PRO505XL, PRO510XL, PRO520XL, and PRO538W The Uniden BC645 is a Rugged CB Microphone that features an 8 foot, extra flexible, coiled cord. Comfortable Ergonomic Design, Rugged Construction, Clear Quality Sound, Built for The Professional Driver. BC645 Features Electret Condenser Replacement Microphone, Wired for 4 pin radios. Trucker tough its everything you expect from UNIDEN. This 4 pin CB microphone is the model that comes with the PRO505XL, and is the factory replacement for that CB radio. This microphone will also work with any radio wired 4 pin Cobra/Uniden, including the following models: PRO505XL, PRO510XL, PRO520XL, PRO538XL, Cobra: 19DXIV MODEL NO - BC645