This is an O-ring kit for the 1st generation TST Flow Thru sensor. 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 Hex Screw replacements * 2 Replacement Hex Screw tools * 1 Philips Screw Driver ATTENTION: If you have generation 2 Flow Thru Sensors then you will need a generation 2 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 hex screws as the anti-theft device then that is a generation 1 Flow Thru sensor.