Magnesium carbonate in a refillable sock. Complies to gym's "no loose chalk" requirements. Also, check out Atomik's Liquid Hand Chalk which also complies! 56 grams. With a few exceptions, a lot of the chalk in the US industry is coming from the same manufacturing plants. So the chalks are often the same. It costs more to screenprint on the bottles as well as it costs more to buy in small batches. At Atomik, we buy in bulk and use the most cost-effective labeling and shipping to deliver the lowest chalk prices in the industry to you.