6075993 PT# 29-7920 Filter Bacterial/ Viral Pulmoguard II Plastic FOR Spiro 50/Bx Made by SDI Diagnostics: Health And Personal Care: Amazon.com: Industrial & Scientific
Inline Carbon Filter 2" x 10", 1/4" Quick-Connect - $4.35
VBMax 33 mm PFT Filter for Custo Med's custo spiro mobile spirometer