The Spiraldots, and pretty much every other eartip are made of silicone, the Xelastecs are made of TPU. I still don't know why these cost so bloody much when your regular China TPU clear case is like 2 bucks, but they are the grippiest eartips I've ever come across. It means that as long as you get the fit right, once they go into your ear, they never slip. You always get a perfect fit, which is great for ANC TWS.
I'm still very much in the honeymoon period with these things so take my words with a pinch of salt. I don't know if the TPU stains and loses its grippiness over time, in which case you're better off with cheaper silicone tips. And I'm not kidding about how much junk they trap, if you have issues with earwax, stay far away. But if you're chin chai and don't mind having a bit of stuff on the eartips (or have just given up on cleaning them every time you take them out of the case lol), the fit on these are unbeatable.