The spirals are no joke, especially how they tighten right in the middle instead of staying uniform the whole way through. It's a pretty intense squeeze, so slower is better here — glad I took my time with it.
Wasn't expecting the tightening in the center to feel that distinct, but it really does grab right in the middle. The spirals intertwine gently at first and then build into something much stronger. Genuinely a step up from the simpler cups I've tried.