41 pc set comes with 20 Lego thin caps, 20 Boston fats caps, and 1 blue Uprok adaptor - Lego thin cap Spray Type: THIN (0.5-1.5″ Radius, clean and solid line) Recommended Uses: detail work, outlines, borders, highlights, hand styles - Boston fat cap Spray type: FAT (3-4″ Radius, clean and solid circular pattern) Recommended Uses: filling in large areas quickly, outlining of large pieces, hand styles and flares - Uprok Adaptor Adapter for male cans with a 1/8″ valve stem (3.2mm) – use all your favorite caps on the new male valves. This adapter makes it all possible.