Adaptation of sophisticated and patented multi-frequency rubber ``Ring-O-Raised`` diaphragm system with ``Superflex`` chrome plated and chestpiece plus 1 pc molded PVC tubing as well plastic retainin
Adaptation of sophisticated and patented multi-frequency rubber ``Ring-O-Raised`` diaphragm system with ``Superflex`` chrome plated and chestpiece plus 1 pc molded PVC tubing as well plastic retainin