Perst-4 Laser IR Aiming Green Visible Laser Sight with KV-D2 Tactical Swtich. Perst-4 IR laser is used to point targets when observing, inspecting and watching small arms shooting at night. The Sotac perst-4 is a small optical mechanical device that forms laser radiation flux. This product is installed on Picatinny rails. The KV-D2 Tactical swtich (in the kit)can be installed on picatinny rails and 1913 rails. Perst-4 contains 2 laser functions. Green Laser light source: wavelength – 635 nm. IR light source: wavelength – 850 nm. Power supply: CR123A (installed) / battery (3 V). Effective range in the dark. Red beam: 300 ± 100 m. IR beam: 400 ± 100 m. Product weight without batteries: no more than 210 g. Overall dimensions: (37? 60? 91) ± 3 mm. The triangular area on the host can switch between visible laser and IR. On the top or side of the host, the round switch is turned on. Turn on through the KV-1P Wire Control Switch. Press the swtich quickly to realize the strobe function. Two small circular buttons on the main unit to adjuest the laser brightness. Fit For: 20mm Picatinny Rail. If any of this is not clear, please reach out to me for clarification.