These mouthpieces are good because they never break or dent , they do not cost as much as silver or gold mouthpieces , and they are good for playing outdoors . Some of the positive features of these mouthpieces are that they are very durable and will not chip nor dent as is the case with metal mouthpieces , they are very affordable compared to metal mouthpieces , and they are commonly used when playing in outdoor conditions as a result of their short `` warm-up '' time .