Remington 870 MK7 Shotgun Mag Tube Weapon Light by Steiner Optics
New interesting and very expensive flahslight which replaces mag cap on Remington 870 shotguns. Good choice if you don’t have magazine extension. Haven’t tested it yet.
The compact, ergonomic design of this 350-lumen mini-light makes it the perfect tactical shotgun light. A shotgun end cap attaches directly into the magazine tube and replaces the factory spring cap.
Integrated puch-button operation
Handheld or weapon-mounted capability
Recoil-resistant white light LED
Robust waterproof construction
High/Low Power Settings
Gorilla Combat Flashlight
There is alternative product with similar features called Gorilla Combat Flashlight, it is sold for $112. Made in Thailand.
You can get more information on Remington 870 Forum.