cover for the TheFloatLife Wire Brush so it doesn't stab all your stuff in your bag and protects the bristles from getting all crushed.  this wire brush is best way to clean your grip tap, 

and now v2 with more curves and reversible for a better grip, although not sure how well that will work.

https://thefloatlife.com/products/tfl-wire-brush?_pos=1&_sid=caa504491&_ss=r