For those who don't know a towel curl is an exercise done with a partner and a preacher-curl stand. You hold the towel using a neutral (hammer curllike) grip with one hand on each end, and your partner puts one hand on the lower part of the U the towel forms. Starting from the bottom, you attempt to perform a curl with the towel while your partner applies enough force downward that you are barely able to perform the upwards curl motion. Once at the top, your partner pulls down on the towel with as much force as they can manage, and you perform a negative as you resist the weight as much as you can. Anyway, they are fucking money for destroying your entire arm. Try them.