Diameter: [1, 1.5] 3.15 in, [2] 3.3 in, [3, 3X] 3.63 in, [3.5, 3.5X] 3.85 in, [4] 4.25 in * Fly Line Weight: [1] 3 WF, [1.5] 4 WF, [2] 6 WF, [3] 7 WF, [3X] 8 WF, [3.5] 9 WF, [3.5X] 9 WF, [4] 10 WF * Material: aluminum, stainless steel * Backing Capacity: [1] 75 yards 12 lb, [1.5, 2] 100 yards 20 lb, [3] 150 yards 20 lb, [3X] 225 yards 20 lb, [3.5] 200 yards 20 lb, [3.5X, 4] 250 yards 30 lb * Recommended Use: spare fly fishing spool