MACK X-CALIBER PINSTRIPING BRUSH SET Part# MAC SET-EXCALIBER4 (4 Brush SET) 0000 Part No. MAC X-0000 000 Part No. MAC X-00000 Part No. MAC X-000 Part No. MAC X-0 What makes the XCaliber special is it s short hair length. Only 1-1/2 vs. the average 2 and 2-1/4 . This shorter length allows greater control for intricate designs as well as long lines. X-CALIBER Series - Short Length Squirrel Hair Stripers are made in sizes 0 00 000 and 0000. Squirrel Hair: Blue squirrel is the most readily available and comes in long lengths as well as short lengths. It is generally used for striping brushes and lettering brushes. Brown or kazan is no longer as plentiful as it was several years ago. It is generally found in the shorter lengths and used for stripers quills and outliners. Both blue and kazan are very soft and fine. They point as well as kolinsky but have very little snap since the hair is not very resilient. Grey squirrel is the hardest to find and the most expensive. It is more durable has more snap and makes a great quill or lettering brush.