Pattern - Thread Theory - Cosmos Trunks

The Thread Theory - Cosmos Trunks sewing pattern is designed for a form-fitting, comfortable boxer brief that moves with you. Featuring no center back seam, a reinforced inseam gusset, and a shaped front cup, these trunks fit like a second skin without rubbing or shifting. Short, athletic legs and a smooth elastic waistband create a streamlined silhouette suitable for wearing under slim-fit pants, gym shorts, or casual wear. Ideal for creating a functional, hand-made underwear wardrobe that combines comfort, style, and durability.

Key Features

• Form-fitting boxer trunks for comfort and support
• No center back seam for smooth, comfortable fit
• Reinforced inseam gusset and shaped front cup to prevent rubbing or shifting
• Short athletic legs with smooth elastic waistband for streamlined silhouette
• Ideal for layering under pants, gym shorts, or casual wear
• Part of the Alpine Outdoors Collection for hard-wearing, classic fit designs
• Teaches precision sewing techniques for stretch fabrics

The Thread Theory Cosmos Trunks pattern is a form-fitting boxer brief with no center back seam, reinforced gusset, and shaped front cup. With short athletic legs and a smooth elastic waistband, this pattern allows sewists to create durable, comfortable, and stylish underwear for everyday or active wear.