Blom-Singer Dual Valve Voice Prostheses, 20 Fr, 12mm.When the primary valve fails, the secondary speech valve is intended to remain viable to help prevent leakage of fluids. The Blom-Singer Dual Valve Voice Prosthesis LF is available with large esophageal and tracheal flanges. Includes nonsterile voice prosthesis for secondary or replacement TEP procedures, with insertion/cleaning accessories.