Well, not 100%. It’s heat resistant enough to be put into the oven right after use. But it’s not meant to touch the stem when heated extensively.
The other day I found some black smear on one of my stems that I couldn’t assign. Later i found those marks at the cap, realizing it got melted a tiny bit. It’s no concern at all as it’s fractions of fractions of a millimeter. This have to happen an awful lot before it turns into a problem.
Btw I was asking myself if this thing can be replaced, but couldn’t find no spare part. Anybody lost it due to breaking or ripping out of the unit?