An underwired bikini top with adjustable straps lets you fine tune the fit across your shoulders and chest which matters because bodies are not symmetrical. Adjustable straps need to be accessible and easy to move which means they should be on the back not hidden or complicated. The ability to adjust means you can customize the support level and the strap placement to your body. Adjustable straps also help with longevity because you can tighten as elastic relaxes over time. The straps need to be secure in their position which means good hardware not sliding adjusters that do not hold. These are the underwired bikini tops where the adjustability is built in as an essential feature not an afterthought.