Arc'teryx Fission Line

Arc'teryx built the Fission line to fix a problem no one else had addressed. Waterproof insulated jackets leaked heat through stitch lines, and the industry accepted it. The Fission Belay Parka debuted in 2003 at 805 grams. It packed 200 g/m² PrimaLoft Sport laminated directly to a 270NR 2-layer Gore-Tex XCR shell. No quilting. No needle punctures through the membrane. That eliminated cold spots at every seam and maintained waterproof integrity.

Why Non-Quilted Construction Mattered

Arc'teryx fused PrimaLoft directly to the Gore-Tex membrane using lamination. They'd perfected this bonding technique on Alpha SV pit zips and pocket flaps since 1998. The process maintained full waterproof integrity while evenly distributing insulation across every panel.

This wasn't a minor upgrade. In 2003, most insulated waterproof jackets used quilted channels that compressed under a pack's hipbelt or shoulder straps. The Fission eliminated that. It is also compressed smaller than quilted alternatives because the laminated insulation doesn't trap air in fixed baffles.

Arc'teryx Fission Belay Parka

The Belay Parka sat at the top of the lineup as a piece. It packed 200 g/m² PrimaLoft Sport with a 270NR 2-layer Gore-Tex XCR shell, a helmet-compatible insulated Storm Hood, and WaterTight zippers throughout. Hip length with a drop back hem. Arc'teryx included a stuff sack. That tells you how compressible this thing was for a fully waterproof insulated parka at 805 grams.

Colorways ran Azul and Yam. The Belay Parka continued mostly unchanged through 2005, making it one of the more stable products in the early Fission years. It served one purpose: keep you warm at the belay station when everything around you is frozen and wet.

Fission SV and AR Jackets

The Fission SV was the heavy hitter. It weighed 1,000 grams for a men's medium with 200 g/m² PrimaLoft Sport and a 300NR/360N 2-layer Gore-Tex XCR shell. A helmet-compatible insulated Drop Hood, reinforced shoulders, elbows, and hips, plus four pockets with laminated zips. Past hip length with a drop back hem. Colorways in 2003 included Java, Sapphire, and Black, available only in XXL.

The Fission AR weighed 770 grams (men's M) with 133 g/m² PrimaLoft insulation. Arc'teryx added 420NR 3-layer Gore-Tex XCR panels in high-wear zones alongside standard 300NR and 360N 2-layer construction. A Stow Hood tucked into the collar when conditions cleared. The 2005 version added reinforced shoulders and smooth knit cuffs. Colorways shifted through Black, Java, Yam, Sapphire, Statue, Molten, Cinder, and Pimento depending on the season and gender.

The Fission LT: Windproof but Not Waterproof

Arc'teryx split the Fission LT away from the Gore-Tex XCR shells by using Gore-Tex Dryloft instead. Dryloft was windproof and water-resistant, but not fully waterproof, which saved significant weight. The Fission LT Jacket hit 550 grams (men's M) with 133 g/m² PrimaLoft Sport and a 220NR/340P 3-layer Dryloft shell. A matching vest weighed just 300 grams.

By 2006, Arc'teryx had moved the Fission LT series to Windstopper Loft construction rather than Dryloft. The Fission LT Hoody appeared at 610 grams with a full Storm Hood and 200 g/m² PrimaLoft. A Fission SV Glove joined the accessories lineup using the same non-quilted laminated PrimaLoft approach.

Fission LT Pant

The Fission LT Pant at 610 grams was designed as a belay-specific piece you'd pull on over your climbing pants when the temperature dropped. Full separating side zips for easy on/off over boots. Adjustable waist, reinforced seat and knee, and 200 g/m² PrimaLoft with Dryloft construction. It paired with the Fission Belay Parka or Fission SV for complete insulated coverage in alpine conditions where standing still meant freezing.

How the Fission Evolved and Eventually Disappeared

The Fission SV survived longer than most of its siblings. By 2020, model 19645 still carried the Fission SV name at $800 CAD and 890 grams, but the construction had changed completely. Coreloft Continuous replaced PrimaLoft. Gore Thermium replaced Gore-Tex XCR. The Descent Line names and the Belay Parka had long since been retired.

Arc'teryx eventually folded the Fission concept into the Beta Insulated Jacket. That model uses 40D Gore-Tex ePE with Coreloft Continuous at roughly 640 grams and $750. The North Face and Rab build competing insulated waterproof shells. Neither matches the two decades of refinement Arc'teryx put into bonded insulation, starting with that first Belay Parka. The Dually Belay Parka from the LEAF program carries forward the most direct descendant of the original Fission concept for military applications.