Another mobility favourite of mine that ends up in a lot of client workouts.
The chest and shoulder muscles are usually tight for a lot of people so this ends up being one of those exercises that looks easy but can be tough to begin with.
I would also recommend starting with a lighter band as this has a bit more stretch to it which can be kinder to the shoulders.
The exercise can also be done with a bar although I find holding the bar can be uncomfortable on people's wrists - where you don't get that with the bands.
This is my, mostly, Personal Trainer musings and information which I hope you'll find helpful!