£4.40 Entonox® Clear-guard Midi Breathing Filter £64.00 Pack of 35 Straight Entonox® Mouthpieces £4.30 Pin Index Flat Key for Oxygen and Entonox® Cylinders £150.00 Bullnose Oxygen Regulator with Multiflow Valve for F Size Cylinders £102.00 Select-a-Flow Meter with BS Probe