Pretty good - Aimtech Warhammer Tactical Full Rail Tri Rail Shotgun Mount

This is a pretty good addition to your 870 if you want to avoid drilling and tapping your receiver. Looks heavy but is hardly noticeable when mounted and is made of a fairly resilient metal. Just know the product you'll receive doesn't match the picture here on the add and is quite a bit shorter. Not a deal breaker for most but won't fit with certain magazine tube extensions and may not be suitable for co-witnessing front and rear sights. It does include the side saddle though. All in all not a bad product if you're willing to do a few extra steps when breaking down.