A FAB (Foam Arsed Blob) is a highly buoyant, attractor trout fly featuring a “Foam Arsed” (or foam-tailed) design, usually built on a compact, bright-coloured, Fritz-covered body. Developed for stillwater competition fishing, the foam rear provides excellent buoyancy, allowing it to sit just under the surface, “washing line” point fly to, keep nymphs from sinking too deep