This cute little mushroom brush is used to brush excess dirt off mushrooms if and when it's your preference not to peel them. Personally I prefer not to peel mushrooms as somehow I perceive them to be more flavoursome with the skins on. A gentle but thorough dusting with this brush will remove any excess soil or dirt and leave them ready to use.
The brush is a small coloured plastic dome approximately 3-4 cm diameter (mirroring the cap of the mushroom) with 2cm long nylon bristles underneath mirroring the stalk. The size and shape of the brush makes it easy to hold in the hand and use. It's a funky little design and a neat item. It's well made, the plastic is robust and looks good as new after many years, and all the bristles are still in tact. The bristles are well designed - initially you'd think soft to the touch, but they are stiff enough to remove the dirt without being too stiff as to damage the mushrooms.
The only problem with the brush is that using it on a large quantity of mushrooms at a time the bristles get very dirty and is not easy to clean at all. I just wash it in the washing up bowl with all the other dishes but over time they're no longer back to the true white of when the brush was new.
We eat a lot of mushrooms and use the brush regularly. The only alternative really which we did previously is to try wipe/dust with kitchen towel which can quickly get messy.
Although its one of those "what on earth did you buy that for?" purchases to some people, it's actually a really useful thing to own. I've just seen that these are up to £8 on Amazon, and I couldn't really argue their case at that price, but if you shop around I think we paid around £3 which is about right.