Replacement battery fits 8 BLU compatible models. Specifications: 850mAh, 3.7V, Li-ion. Compatible with: Siemens Rexton, Siemens WL200AP, Bluetooth Remote, RCU, SGI-WL200AP, WL200AP and 2 more compatible models. Replaces: Siemens 21221-10296051, BLU 21221-10296051, REXTON 21221-10296051. BLU replacement battery designed for Remote Control devices. Perfect for professional or everyday use.