I've tried many supports over the years and the others are right they can affect span, depending on type of support and your hand.
My favorite is the Moro Pro-Release , the Extended Version and didn't really affect my span.
If you never used one before, one thing to remember is don't let it control you.
If you don't watch it they can pull your hand around the ball and cause you to top the ball.
oh and wear a sock under it, you can sweat a lot wearing them.