Why are there small fighting/cork butt ends on euro-type nymph

Cork Butt End Plugs - Custom Fly Grips LLC

Euro Nymphing Gear for 2021 - Fly Fisherman

56 - Euro Nymph Basics

Cork Fighting Butts - Custom Fly Rod Crafters

You can find my review of these rods at this link. , Thanks to Austin Curtin for several of the product photos., A new favorite here at Tactical Fly

Adams XTZ Euro Nymph Rod

twigandstream – Twig & Stream Fly Fishing

The most demanding conditions require a different kind of tool. Strong head wind - Casting at distance - Long heads or Heavy sink-tips The IGNITER is tuned to handle the most technical of conditions. Not a rod for the everyday angler, the IGNITER is equipped with and ultra-fast action high line speed taper to carry large amounts of line at distance with wind cutting performance. Perfect for long Traditional or scandi lines and/or winter Skagit heads with heavy sink tips and flies.

Sage Igniter Fly Rod 9' 7wt

Cork and EVA Fishing Rod Butt Grips

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Grips, Rings & Fighting Butts - Fighting Butts - Custom Fly Rod