I use TEL-TRUE thermometers. I have a large commercial size smoker, a gas vertical smoker and a vertical wood/charcoal smoker (to mention a few) and they all have TEL-TRUE therms. Tel-TRUE guarentees them to be within 1% accuracy. (maybe its 2%. Not sure) So if your cooking at 225 deg, your therm will be within 2 1/2 deg. TEL TRUE's are not cheap but neither is a 5 lb beef brisket.