A pair of Bluetooth tire pressure gages replace your tire air valve caps. Using our free APP, you can connect wirelessly VIA Bluetooth to your smartphone. At any time, you can monitor the tire pressure on front and back tires on your smartphone. Special locks are provided to lock the units in place. Carries one-year parts and labour warranty. Caution: TPMS installed on top of tire stems, such as SRT200, SRTP300, SRTP340 and SRTP630, increase the pressure in the tire stem. Hince, not recommended for tires with plastic or rubber stems. Please see SRTP400 for inner TPMS.