410 Microlight is West System's fairing filler: a microballoon blend that turns 105 epoxy into a dark red-brown fairing compound that sands easier than anything else in the line. For skimming and shaping large areas above the waterline, it is the West filler to reach for. Thicken mixed resin to a peanut-butter consistency, trowel it on, and knock it down with 80 grit once cured; the low-density microballoons are what make the sanding easy. Keep it off high-temp dark surfaces and out of below-waterline barrier-coat jobs; West's own guidance routes those to 407 or straight epoxy. Blending your own fairing mix costs a fraction per quart: phenolic microballoons, 3M glass bubbles, or Q-cells in your resin of choice, proportioned with the fairing filler calculator. The comparison below shows all four options.
