MMA Rash Guards are a vital for no-gi BJJ and MMA as they keep moisture away and limit skin-on-skin contact. Not only it will keep you more dry but also help prevent contraction of skin born diseases. Rash guards are also required for no-gi IBJJF competition. Another popular way of using a MMA Rash guard is under your gi as they will still limit skin-on-skin contact and will also minimize the rug-burn like effect from the gi.