West System Adhesive Fillers vs. Fairing Fillers

Fillers are used to thicken the basic resin/hardener mixture for specific applications. Each filler possesses a unique set of physical characteristics, but they can be generally categorized as either Adhesive (high-density) or Fairing (low-density).

Adhesive filler mixtures cure to a strong, hard-to-sand plastic useful in structural applications like bonding, filleting and hardware bonding.

Fairing filler mixtures cure to light, easily sandable material that is generally used for cosmetic or surface applications like shaping, filling or fairing.


403 Microfibers
403 Microfibers, a fine fiber blend, is used as a thickening additive with resin/hardener to create a multi-purpose adhesive, especially for bonding wood. Epoxy thickened with microfibers has good gap-filling qualities while retaining excellent wetting/penetrating capability. Color: off-white.

  • eboatworks Price 6 oz. Microfibers $10.20 Buy Now
  • eboatworks Price 20 oz. Microfibers $18.70 Buy Now
  • eboatworks Price 20 lb. Microfibers $149.95 Buy Now

404 High-Density Filler
404 High-Density filler is a thickening additive developed for maximum physical properties in hardware bonding where high-cyclic loads are anticipated. It can also be used for filleting and gap filling where maximum strength is necessary. Color: off-white.

  • eboatworks Price 15.2 oz. HD filler $12.50 Buy Now
  • eboatworks Price 45.6 oz. HD filler $25.95 Buy Now

405 Filleting Blend
This strong, wood-toned filler is good for use in glue joints and fillets on naturally finished wood. It mixes easily with epoxy and lets you create fillets that are smooth and require little sanding. Its color is a consistent brown, so 405 can be used to modify the shade of other WEST SYSTEM fillers.

  • eboatworks Price 8 oz. Blend $12.95 Buy Now

406 Colloidal Silica
406 Colloidal Silica is a thickening additive used to control the viscosity of the epoxy and prevent epoxy runoff in vertical and overhead joints. 406 is a very strong filler that creates a smooth mixture, ideal for general bonding and filleting. It is also our most versatile filler. Often used in combination with other fillers, it can be used to improve the improve strength, abrasion resistance, and consistency of fairing compounds, resulting in a tougher, smoother surface. Color: off-white.

  • eboatworks Price 1.7 oz. Silica $9.95 Buy Now
  • eboatworks Price 5.5 oz. Silica $18.95 Buy Now


407 Low-Density Filler
407 Low-Density filler is a blended microballoon-based filler used to make fairing putties that are easy to sand or carve. Reasonably strong on a strength-to-weight basis. Cures to a dark red/brown color.

  • eboatworks Price 4.7 oz. LD filler $12.95 Buy Now
  • eboatworks Price 12 oz. LD filler $31.95 Buy Now
  • eboatworks Price 14 lb. LD filler $249.95 Buy Now

410 MicrolightTM
410 MicrolightTM is the ideal low-density filler for creating a light, easily-worked fairing compound especially suited for fairing large areas. Microlight mixes with greater ease than 407 Low-Density filler or microballoons and is approximately 30% easier to sand. It feathers to a fine edge and is also more economical for large fairing jobs. Not recommended under dark paint or other surfaces subject to high temperatures. Cures to a tan color.

  • eboatworks Price 2.3 oz. ML filler $18.95 Buy Now
  • eboatworks Price 4.2 oz. ML filler $29.95 Buy Now
  • eboatworks Price 4 lb. ML filler $235.95 Buy Now