The insulation keeps the cold inside. You can always increase dilution by waiting or shaking more, but insulation makes it easier to hold and more flexible. The threaded lids work well, they could have a better taper to reduce cross threading, but they are fine and seal positively with the gaskets. They don’t leak much on removal, making it easier to use and clean.The size is good for two cocktails. The strainer and measuring cap are fine, though I usually use a jigger, it’s nice to have the marks just in case (edit to add, I am using the cap to measure more, after a few weeks…it is handy).More color choices would be nice.A much better shaker, and better value, than many other insulated shakers, I think. I’ve made daiquiris, margaritas, whiskey sours and whiskey smashes, all fine. Recommended.