I would give this 3.5 stars so I am rounding up to 4. But this is a 3.5-star review.
This item basically consists of a plastic stock butt piece, and two carbon fiber tubes that connect together with a plastic coupler, with another plastic piece that connects to the end of the barrel. These latter two pieces have strong magnets on them that hold two plastic controller cups. using set screws that accept an allen key on one end and have a sharp point on the other end. The set screws thread into little holes on the plastic pieces, butt up against the carbon with the sharp end, and ostensibly keep everything in place.
I did have some issues with this process. The screw hole on the butt of the stock didn't thread properly, and so the tube that went into the stock didn't seat correctly and was wobbly. Additionally, the piece that joins the two tubes together is a little "rocky" when the set screws are screwed in - there is a sweet spot for the set screws and if you go too far the carbon is very easily "crunched" which results in more rocking. My solution for this was just to epoxy everything together, and it's solid as a rock now. No big deal.
The two smaller plastic pieces go in the middle of the two carbon tubes (joining them together) and on the far end (opposite the butt). These pieces have very strong magnets on them. The magnets connect to the little cups that hold the controllers, and these are well-designed. The controllers sit nicely in them with a hole for the strap at the bottom. With practice you can somewhat easily "rock" the whole cup off of the base magnet if you need to use the controller independently.
When your weapon is has a full magazine with one in the chamber, this stock works fantastic. Have used in Pavlov, Gun Club VR, and Lambda1VR HL port. In Gun Club you'll need to purchase the "flashlight with grip" for your rifles for proper hand position. I MELTED the assault rifle challenge in Gun Club VR with this thing, all 40 levels, on semiautomatic, with the red dot sight (no laser). Walked right through it, and I'm no marksman. It is that good.
Where you run into an issue is reloading, and any other actions that require the second hand to come off the front of the gun. You've got to get really good at detaching the whole off-hand controller cup from the magnet base, grabbing your magazine from your hip (or pulling the slide or whatever), and snapping it back on the magnet base quickly, without being able to see what you're doing. In Gun Club I just get whatever the largest magazine size for the weapon is. Cocking shotguns is a challenge as well.
So - some QC issues but easily fixed with some glue (for me). Fantastic for aiming with two-handed weapons; really brings the feeling of holding a rifle to life in VR. Some issues/tedium around easily reloading/cocking weapons due to the off hand being fixed to the barrel with a really strong magnet. All in all, I still use it, and would recommend it.