I own these gloves in 16 oz and say they can definitely be used for sparring. Overall, they're designed to be Fairtex's all-around model. While it's recommended to have separate sets for both bag work and sparring, having one pair of these gloves in a middle weight range between the two functions is a cost effective alternative to solve this problem. For sparring, I recommend either the 14oz or 16oz gloves since most people spar comfortably within this range.

Higher weight corresponds to greater padding. If your partner is cool with it, the lowest you could go at is 12 oz for heavy sparring. I've never tried up to 18oz but I feel like it'd be so cushioned that it'd be counterproductive for training. You're training to learn to take punches here and there in sparring, so the extra 2oz might do more harm than good.

Do not get 12 oz if you plan to spar. If you need sparring gloves get 16 oz. 14 oz sparring gloves are for people who weigh less than 150 lbs usually or are experienced fighters.