Keeping a few spare large arbor spools handy makes changing lines on the fly a snap.
Clearwater® Large-Arbor Extra Fly Spool
Fly reel wychwood RIVER & STREAM BLACK
Fly Reels up to line #3 ▻ buy at Rudi Heger
Fly Reel Spare Spools, Extra Spool for Fly Reel
Traper
Excellent Fly Reels: Sage, Redington, Hanak ▻ buy at Rudi Heger
Redington Run 7/8 Spool Black
Spare Spools: Shop Fly Reel Spools from $35+