This is a compatible replacement battery (Cameron Sino part CS-SHD440SL) listed by the supplier for the EPOS Adapt 360 Bluetooth headset. The Cameron Sino part itself is documented as a replacement for the Sennheiser battery parts AHB622540N1 and CP-SN40 used in the Sennheiser HD 4.40 BT, HD 4.50 BTNC, Urbanite XL and Momentum 2.0 and 3.0 wireless headphones. When a wireless headset's battery has aged and no longer lasts a full day, fitting a new cell restores playback and talk time without replacing the headset. The battery is a 3.7 V lithium-polymer pack rated at 600 mAh (2.22 Wh), measuring about 42.4 x 24.5 x 5.8 mm and weighing roughly 36.5 g, with a short lead and a three-pin connector. Fitting requires opening the earcup, so it suits technicians and confident owners. It is an aftermarket part produced by Cameron Sino, not an original EPOS component. Before ordering, confirm that your headset's existing battery matches this part number or connector, especially for the Adapt 360, which is not named in the battery maker's own compatibility list.