I've struggled for a number of years to get a suitable shoulder rest for my big 17" Viola. Firstly, getting a shoulder rest to fit was a struggle in itself, but the main problem was that the shoulder rests I was using weren't offering any support at all and weren't very far away from just not using a shoulder rest at all!
The Bonmusica 17" Should Rest is a revelation. It is fully adjustable in every way, so you get get it to sit comfortably on the most awkward shaped violins (and shoulders). The shoulder support itself is made of a firm but malleable metal which allows the player to subtly mould the rest to the shape of their shoulder. Genius!
You're able to obtain a snug fit which makes the Viola feel comfortable and secure. This is first shoulder rest that has passed the "just using your chin with no hands" test.
A must buy for any string player, but particularly if you have a larger than average Viola. Also a very good price.
Thoroughly recommended!