This is an O-ring kit for the 2nd generation TST Flow Thru sensors. When you change the batteries in your Flow Thru sensors you will need this kit to replace the O-rings, screws, and valve stem gaskets if needed. This kit also includes a Philips screwdriver that is the perfect size for the screws that you will need to remove to replace the batteries. This kit has all the replacement pieces for 6 sensors. If you are changing the batteries in more than 6 sensors then order as many kits as you will need to get to your number. This O-ring kit includes: * 6 O-Rings * 6 Valve Stem Gaskets * 12 Replacement Screws for the Battery Cover * 6 Brass Hex Nuts * 1 Philips Screw Driver ATTENTION: If you have generation 1 Flow Thru sensors then you will need a generation 1 O-ring kit. Be sure to look at the pictures on this listing to match up which flow thru sensors you have. If you have the brass hex nuts as the anti-theft then you have generation 2 Flow Thru sensors.