Primary Standards for field Calibration, these unique units are:

• Portable (Weights: 1.5 oz; 2 oz; 8 oz.)
• Self-contained
• Leakproof
• A1l plastic
• Provide instant soap bubble movement by depressing central cylinder 1/4".

Flow is established by timing bubble and reading off flow from a special "time" chart attached to the flow meter barrel.