Very easy to customize the scroll bar and it looks great on the website. Also great support, helped me with all my questions.
The Boozy Button
I am using this app to show a progress bar on top of my product page since it has lots of descriptions! Love how easy it is to setup and you don't even have to leave the shopify admin! love it! =)
This app helps a lot with boosting your conversion rate! I would recommend this app for every type of store!