All standard valve stems (Schrader) have a removable valve core in the center. Use the valve core removal tool, that is included with all Tire Sealant Kits, to remove the valve core. Then the injector threads directly to the valve stem for easy installation and measurement.
*Note: To accurately measure pinch or kink the hose at the tip of the injector, fill injector to desired amount and then un-kink/un-pinch the hose to allow measured amount to flow into the tire. Use the injector plunger to clear the injector if it backs up.