Great little add on to my Peak vise. I had a material spring on an old beginners vise years ago. When I upgraded to a Peak vise, it didn’t come with a material spring and I didn’t even miss it. But as I started getting into more fly patterns with multiple materials (especially spooled materials) everything kept getting in the way. This material spring fits really well and gets the job done. Comes with 2 springs…small and large (medium ish). The spring that came already on it has work well for me so far.