The Westone TRU Solid Adapter provides the best noise attenuation and the highest noise reduction rating (NRR) in the line of Westone musician ear plug filters. They do cut the high frequencies, however, providing less accurate sound than the TRU musician's filters do, so these are best used when blocking out sound is the primary goal. These solid adapters can be used in any ear plug that works with Westone TRU filters - the most common of which are the WM series of filters, such as the WM10 or WM16. Just snap the filter out and the solid adapter in for powerful hearing protection. Westone Part#: 63026 Westone TRU Solid Adapters are Compatible With: