Typically 12 - 16 oz gloves are used for the heavybag. But even more important than that is how well made the gloves are, some good brands are:
Winning (Absolutely the best of the best, if you have the money go for it)
And only the top product lines in Ringside, Title & Everlast. (Don't buy from their cheap product lines, not worth it)
Don't go under 12. I use 14 oz gloves for sparring and the heavy bag. they go up to 20 oz if you're a big guy.
12-16 is ideal. I prefer 16 oz. though because when you use the sparring gloves, 8oz. You are actually faster. I think it's an effective training method.
14 OZ gloves.
I suggest you buy a good quality one too. Don't buy everlast.
Buy Winnings.
http://ezinearticles.com/?How-to-Choose-...
I have no experience In a gym or any training In fighting or this sort of conditioning.
I'm doing It strictly as means of conditioning and getting some muscle In the areas worked.
I read about the benefits of heavy bag training and youtubed how to throw proper boxing throws, just so Id know a little bit.
But I learned boxing gloves have different ounces.
What's the best oz to get?