The Thorium SV vest combines the exceptional warmth of a down jacket with the freedom of a vest. This gives it a versatility to perform as an outer layer in dry, moderately cold weather, or as a lofty midlayer for more severe cold. Lofty 750 fill European grey goose down delivers exceptional warmth for little weight, is durably resilient, and packs easily. The vest’s sewn through construction reduces weight and increases packability. The outer is soft, durable Arato™ 40 nylon, a lightweight material that withstands abrasion, packs compactly and has a DWR finish to repel moisture.ATTENTION to DETAILSA vest seems simple, but requires as much attention to detail as any piece Arc’teryx builds. Arc’teryx Down Composite Mapping technology combines the goose down insulation with panels of Coreloft™ synthetic insulation in areas prone to moisture. The Thorium’s Athletic fit is streamlined enough to fit under a shell, but leaves room for layers underneath should it be worn as a standalone. Gaskets are placed under the arms to block drafts, an internal dump pocket stows gloves or a toque, an internal zippered pocket secures a smartphone or wallet, and two insulated zippered pockets warm the hands.