Hi Chuck,
Those dial ones might be good for whipping across the room to try and ding the clerk that sold you them but that's about the only use I would ever put one to.
You can get a good digital for £10 and a good in/out/hygro for about £15 on ebay or in some online shops.
Anything claiming to be 100% accurate generally doesn't understand one of those terms.
Theres also the fact that only the probe ones allow you to actually check the temperatures inside the hides where the snake is actually going to be.
Spend the extra dough and stay away from the dials unless you want to know the wrong temps half way up the tank wall.
dr del