tel-tru are very good, but don't make the mistake of thinking that the temp of the grill is the same as the temp on gauge.mine runs about 30 degrees hotter than the real temp of the grill. just my 2 cents worth
Make sure that you place the chamber probe at grate level -some come with a clip that you attach to the grate and then place you probe in the clip. I just run my chamber probe through a potato that I cut in half widthwise. I've seen some "Lang-a-likes" (Lang clones) that have had temp gauges placed at grate level just to the side of the door opening in order to get a more accurate chamber temp at food level.