To use, push it the lock like normal. Pull up on the shoulder belt and it will lock so there is no slack and as hard as you want to pull up, is as hard it will lock your lower torso to the seat. You won't move if you don't want to.
How did it work? I really liked it. For roads like Tail of the Dragon, it's the perfect thing short of a full harness. I also am using it for autocrossing.
I find I like it enough, that I leave it on for my regular daily driving around town.
There is one downside. I am a little more careful about unlatching the belt and flinging it to the side, since it now has 5 ounces of metal attached to it and could mar the inside of the door. It's not that bad as it sounds, but you just don't want to throw the belt open.
We sell it for $34.95 plus shipping. If you can, the best thing is a full 5 point harness. But if you can't, I think the CG-Lock is a very good solution.
We have seen video of the crash testing of a dummy on a sled with and without the CG-Lock. Impressive.
Great Product! I've used one in both my C32 AMG and WRX on the track and autocrossing and they clamp you in the seat very nicely. Easy to take on and off so you can move it from car to car with no problems.