I've tried the two and they both work better and shoot straighter than the stock bolt. The black bolt is almost the same but has different groove patterns to make it shoot straighter. I love the red bolt. It's venturi head cushions the ball and makes almost no breaks. It shoots a lot straighter also!
May be overpriced about $15 and they should change the black bolt to a new one that has more advantages to it like the red bolt!
they'd be great if they cost $35. But since they cost 50, I only suggest getting them if you have that kinda money to throw around!