I think a lot of people like acetate for it's retro' feel and so many brands have based their whole aesthetic on acetate frames, even more have adopted a simplistic approach to this material; "we'll design a few nice shapes, cut them out, polish them and then assemble them". Not RES/REI. They used their skill, teamed up with the best workshops and the most renown acetate material manufacturer (Mazzucchelli in Varese, of course!). This is how this material is made.
Then RES/REI started experimenting with this material in their workshop, pushing the limits of its versatility by making it super fine, bonding different patterns, milling away the layers... And here are my favourite experiments.