Ventus Respiratory TR2 Head Harness Strap Small. This strap system is designed to work without a helmet or while wearing a baseball hat. The straps will also fit under most Helmet systems if needed. Specifications for Ventus Respiratory TR2 Head Harness Strap: Manufacturer: Ventus Respiratory Quantity: 1 Age Group: Adults Last Chance: Yes Package Contents: Ventus Respiratory TR2 Head Harness Strap Ventus Respiratory TR2-STPACC-03: TR2 Head Harness Strap Small