The replacement mouthpiece stem tip is the best product for contingencies in case yours clogs up or gets lost. The replacement tip is tailor-fitted for the Air, Air 2 and the Solo and Solo 2. If the glass stem is undamaged but the plastic tip is already fractured or cracked, this is the perfect replacement product. You don’t have to buy the whole set, and it will only set you back a few dollars. Replacing the tip is as simple as screwing it into place. Another reason to replace your plastic tip is if there’s already discoloration or discharging a pungent smell.