10mL Recovery Flask Insert, Anodized ORANGE Aluminum, OptiTherm (for use with OPT100). Optitherm blocks provide a SAFE and cost effective solution for replacing your existing oil baths and heating mantles. The innovative PTFE shield on the unit reduces the exterior exposed surface temperature by as much as 100C. For example, the PTFE shield would be approximately 80C on a 100mL flask that is heated to 180C. The OPT100 is used for 100mL round bottom flasks.