Atos Medical Inc Provox HME Cap Matt Titanium is a dome-shape titanium ring that allows use of the special Freehands HME cassettes without the Provox Freehands HME valve unit. The HME Cap is snapped onto a Freehands HME cassette and then used like a regular Provox HME cassette. Although the HME Cap lacks the benefits of a lid/spring valve mechanism and side openings (found in regular Provox HME cassettes), it does allow the stoma to be closed manually for speech.