Exactly what i was expecting - FAB Defense GLR16 with a GCP Cheek Riser and GPCP Picatinny Rail Adaptor

I wanted a buttstock with a pic rail on it... and there are very few options available. This is perhaps the only one in current production, and almost certainly the only one available in FDE. Why would anyone need a buttstock with a rail? Well, if you get a nice Anker USB battery for your thermal optic, and a 3-D printed holder for it, and you can find a pic rail attachment that will work with that holder, then you'll have the option of being able to mount the battery to your buttstock. What's nice about this stock is that both sides have the pic rail (unlike the out-of-production CAA buttstock that only had a rail on the right side), so you at least have the option of right and left-handed operation. The rails are both at a slight angle, as opposed to being completely parallel with the stock. Not that this matters for my particular application.

I believe the buttstock is designed to be "universal" in that it will work with milspec and commercial spec buffer tubes (AKA receiver extensions). That means it will slop around a bit on your milspec tube. To get around this, I put a single strip of 20mm wide/1mm thick sealing foam tape (uxcell brand, available on Amazon) inside the stock tube, lengthwise. This pads it just enough to eliminate the wiggle, without making it difficult to change the stock position. I learned this trick working with the aforementioned CAA stock, in a prior application.

The cheek riser is useless, which is why I don't give the stock 5 stars. I bought this stock knowing it would be useless, and it's easily removed. You'll need a set of metric Allen wrenches for that job.