This Heat-On insert is suitable for heating 150 ml round bottom flasks. For optimal use it is recommended that you buy the Multi-Well holder together with safety lifting handles. The maximum temperature for continuous use is 260 °C. In order to measure this precisely with a temperature sensor, a small hole is provided on one side of the Heat-On Block. This Heat-On insert is suitable for heating 150 ml round bottom flasks. For optimal use it is recommended that you buy the Multi-Well holder together with safety lifting handles. The maximum temperature for continuous use is 260 °C. In order to measure this precisely with a temperature sensor, a small hole is provided on one side of the Heat-On Block.