Tabs Studio

In my opinion, the idea of this app is brilliant! It allows you to create tabs in a very neat way for your products page (you can use it for different purposes as well such as creating shipping policy, FAQs..etc).

At costs of no more than 6$, other size chart application can cost you multiples of that amount easy. Even better, the tabs content is part of your store theme and page, and you do not see the delay in loading that you experience with other apps.

A point to note, is that yes different themes will have different layouts and with this application you might not get the 100% just by clicking the install button, but the developer seems to be very genuine and helpful to get any issues fixed.
*Always remember to keep a backup of your theme in case you need to revert to a stage before any coding updates

I believe this is a must have app for any store.