I encountered this sentence from some NSFW material. The context is that a couple was about to begin a sexual intercourse. A girl was putting a condom on her boyfriend's straight erect penis. She commented
実際はこれくらい皮{かわ}がたわむ感じなんですね
I am uncertain what 皮がたわむ means here. I think 皮 likely refers to condom's rubber skin and たわむ refers the stretching of that skin?