Walther Multi-Reticle Red Dot Sight (MRS). These are very nice and compact!

Walther Multi-Reticle System (MRS) specifications:

• Red dot
• 7 brightness level
• 4 Recticles
• Weaver Mount
• 7 brightness levels
• 4 reticles
• 1/3 MOA
• Windage & elevation adjustments
• 17 yds field of view @ 109 yds
• 23x34mm lens
• Weaver mount
• 3.25" overall
• .25 lbs.
• Uses 3V CR 2032 battery (included)
• Includes lens cap & 2 Allen wrenches