This is a LaserMax Battery, model LMS-392.
Optimize the performance of your LaserMax Guide Rod Laser sight by installing a fresh set of batteries at least once a year. Reliable" lightweight and powerful" LMS-392 Silver Oxide batteries operate flawlessly across a wide range of temperatures" feature a 5-year shelf-life and are sleeved to ensure quick and trouble-free installation. Please refer to the LaserMax Operator's Manual or Battery Compatibility Chart to confirm correct part selection.
Features:
Battery for SIG 220/226/228/229 guide rod laser