You'll need to get valve stems from a GM dealer. The TPMS in the cobalts are a two piece design. The valve stem has a brass extension off the bottom that the actual sensor is mounted to. A single torx style screw retains the sensor to the stem.
2006 LS coupe, manual, Victory Red
Sportlines, FE5 struts, shocks, front swaybar, Progressive 22mm rear swaybar, Airlift load assist rear airbags, TWM ST shifter, smoothed TB, LSJ exhaust, debadged, demudflapped, Yokohama AVID Touring P195/60R15's. Soon to come 17x7 Motegi Tracklight 1.0. Best to date 15.402 at 90mph
"No friend ever served me, and no enemy ever wronged me, whom I have not repaid in full."
Lucius Cornelius Sulla