This is a Crimson Trace Corporation Laserguard known as the Laserguard Pro, model LL-802.
LL-802 Laserguard(R) Pro(TM) for Springfield Armory XD-S is a powerful red laser sight and 150 Lumen LED white light in a single compact unit. Designed specifically for the XD-S platform" this illumination and targeting product is activated with Crimson Trace's famed Instinctive Activation(TM)" which activates the unit with a normal firing grip. LL-801 offers four modes of operation: Laser + Light" Laser Only" Light Only" and Laser + Light Strobe. The unit features a Master On/Off Switch" is completely user-installed in moments" is adjustable for windage and elevation and offers 2 hours of battery life.
Features:
Front activation
Red laser
Factory sighted at 50Ft
.5 inch diameter at 50 feet