While gloves and mitts are used to protect our hands, Cover Mitts are used to protect the gloves and mitts.
Cover mitts can absorb the brunt of the abuse, are reversible (to extend their life), and you can put a higher temperature cover mitt over a lower temperature glove, essentially extending the temperature rating of the glove.
Cover mitts do have their drawbacks, though. You will loose some dexterity (especially when worn over gloves), and while the cover mitts are reversible, if you put them over a non-reversible mitt or glove, it will result is an additional slight reduction in dexterity.
(Please note that the Kevlar® cover mitts are smaller than the Zetex® cover mitts, and are made to fit over the Kevlar® gloves, while the Zetex® cover mitts are made to fit over the Zetex® gloves)
