This is review of a very good tactical upgrade for Remington 870 shotgun: Streamlight TLR-2 Flashlight/Laser combo. I have installed it using CDM Gear BMT clamp with picatinny rail. I think this is the best way to attach Streamlight TLR-2 or Streamlight TLR-1 to Remington 870.
I really like this flashlight/laser combo, it is lightweight and easily attaches to a rail. TLR-2 is low profile and doesn’t stick out much. Streamlight TLR-1 which doesn’t have laser is even smaller.