You'd be better getting some proper 10-16oz gloves. Those ones you linked will kill your hands doing bag work. The finger loops will slice the skin between your fingers and you'll catch your knuckles on the bag. Unless you're prepairing for an mma match, there is no need to practise grappling with 4ozs on. Not much point in doing pad work with little gloves, get some heavier ones and speed your hands up.
All in all, Do not buy them.
NYBA Champ @ 170!