I got 2 K-31-K drivers from Klipsch...they are not K-31-E. In fact they are doped paper made in China. The E is graphite composite, or carbon composite I believe. A polymer graphite composite cone. rubber surround. The K driver fits, like others, but are NOT a similar driver. Klipsch failed to inform me. I have 2 good K-31-E, and 2 good K-31-K. I have looked and looked for a driver, and for services to fix the voice coil in the 2 blown K-31-E's I have. They work but were overheated and scrape the magnet gap. I may just give a go at repairing them myself.