Protects threads, has O-ring holder, looks cool, strong.
I got this just because it was at my proshop. The weekend I went 'balling and my co2 tank roled out the car and landed on the thread protector. There was no damage to the tank but minor scratches, and the thread protector also only had a few scratches. Also, this weekend, I went to my friends, dads house to go paintballing. Well, my o-ring blew and I forgot spares, but because I brought my protector, I had an extra one.