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. Specs Type West System fairing filler, microballoon blend Resin epoxy (West System 105) Color dark red-brown Sandability easy Density class light Best for large-area fairing above the waterline; not below the waterline Sizes 2 oz, 5 oz, 4 lb bag Origin USA Pick 410 when you are already on the 105 line and want the filler with West's own data sheet behind it: the easiest sanding and the least added weight in the system, for skim coats and shaping over big topside and deck areas. Keep it above the waterline and off surfaces that see high heat; West points those jobs to 407 or neat epoxy. If you blend your own from phenolic microballoons or 3M glass bubbles you pay less per quart and give up the West mix charts. Full lineup in West System; filler choice by job in the marine filler types guide.
