From the Griot's Garage Catalog:
100% BOAR'S HAIR CAR WASH BRUSH. A SAFE WAY TO CLEAN
This brush is probably the safest way to clean surface grime from your car's exterior. Boar hair is the only natural hair that can keep its shape without falling limp when soaked with water. Other "horse hair" brushes are stiffened with nylon which, like polyester, can scratch your surface. Manufacturing this brush is very time consuming. First you have to catch and shave a boar! Then each hair is hand collected, lined up with the split ends out and placed by hand into the hard plastic block. The ends are then flagged (splitting the ends again) to make them even softer. Just a quick shake in water will free the dirt, letting it drop to the bottom of your bucket. I use it for windows, trim, and all painted surfaces. 12 inches long and made to last years. Manufactured in the U.S.A.