Is your Plantronics CS50, CS55, or CS60 wireless headset dying too quickly? This 2-pack of replacement batteries from Kastar will give it new life. These are brand new, high-quality batteries designed specifically for those Plantronics CS-Series models (also fits CS-55PLT). They replace OEM part numbers 64327-01 and 51000100. Each battery is white and measures about 35.35 x 21.07 x 4.37 mm – a perfect direct fit. Buying a 2-pack is smart: use one now, and keep the other as a spare so you're never caught with a dead headset during an important call. Great for office workers, call center agents, or anyone who relies on their Plantronics headset daily. Replacement is usually simple – just pop open the old battery compartment. Save money versus buying a whole new headset. Keep your communication clear and uninterrupted with fresh, reliable power.