With four way stretch and an 18" outseam for ultimate mobility, quick drying fabric, and a timeless silhouette, the Block Party Boardshorts 18" has been a staple in lineups for years â for more than a few reasons. Stock up for summer now. Features 94% polyester / 6% spandex with DWR coating 18â outseam with straight leg Block party stripes Back pocket storage with velcro Icon woven label Imported Men's Block Party Boardshorts 18" in Light Blue, Size 31.