In the old, old days, when they used to fight with four ounce gloves, they sparred with eights. I don't think they ever do any more. The last time I really watched a pro prepare for a fight, it was the guy that fought DeLeon on the undercard of Marquez/Barrera...his name escapes me...but I watched him train 8 or 9 times over three weeks and he always sparred with big gloves.