Kingfisher XL Waterproof Slim Fly Box with Slit Foam Review (2026)
Updated September 21, 2026 · Research-based review
Our verdict
The Kingfisher XL is a slim but large capacity waterproof fly box, built from clear ABS with a rubber gasket seal and stainless hinge pins, holding more flies than most slim boxes while staying easy to pocket. Its bigger XL footprint may not fit smaller chest packs, and its slim depth still squashes the bulkiest foam dries.
Kingfisher XL waterproof slim fly box with slit foam, a large-capacity slim box for anglers with many patterns.
Price range: $ (Budget)
What we liked
- + XL size holds a big selection while staying slim
- + Waterproof design keeps flies dry on rainy days
- + Slit foam grips flies securely
Trade-offs
- - XL footprint may not fit smaller chest packs
- - Slim depth squashes bulky hoppers and big foam dries
Who this box is for
This box is aimed at anglers who carry a wide selection of patterns but do not want the added depth of a bulky standard fly box, since the XL slim design spreads capacity across a larger footprint rather than more depth. That makes it a good fit for anglers who fish varied water and want dries, nymphs, and smaller streamers all within one box, and who are comfortable with a box that is wider than average in exchange for staying slim in a pack. Anglers who mostly carry a handful of patterns, or who use a compact chest pack with limited room, are better served by a smaller box than this XL slim option.
Build and waterproofing
Kingfisher builds this box from clarified, strong ABS plastic with a clear lid, so flies are visible at a glance without opening the box, similar to the clear lid approach other slim fly boxes use. A rubber gasket seals the lid to keep the box essentially waterproof and buoyant if it ends up in the water, while high density slit foam inside grips fly hooks securely so patterns stay in place rather than shifting loose. Stainless steel hinge pins are used on the lid, which resist rust over repeated exposure to river water better than plain steel hinges would, and a snap tight latch keeps the lid closed during normal handling.
Capacity and everyday carry
The XL sizing gives this box more slit foam area than Kingfisher's standard slim boxes, which is the main reason to choose it over a smaller option if you carry a broad fly selection on the water. That larger footprint is still slim rather than deep, so the box slides into a vest pocket or pack pouch reasonably well, though its length and width mean it will not fit every compact chest pack designed around smaller boxes. The slim profile does limit how much depth is available for bulkier tied flies, so very bushy dries or large foam patterns can compress more than they would in a deeper box.
How it compares in the site's fly box guide
In the site's roundup of waterproof fly boxes, the Kingfisher XL ranks fifth of eight, tied closely in score with the Aventik small two pack, the Maxcatch 4.1 by 3 by 1.3 inch box, and Maxcatch's larger 4.9 by 3.9 by 1.7 inch box, all clustered together just behind the C&F Design and Dr. Slick large boxes. Within that tightly scored group, the Kingfisher XL's advantage is its larger flat capacity for a slim profile, while the Maxcatch boxes lean more compact and the Aventik two pack offers two separate sealed compartments instead of one larger one.
Bottom line
The Kingfisher XL is a solid choice for an angler who wants one slim but roomy box to hold a wide fly selection without adding much depth to a pack, backed by a rubber gasket seal and rust resistant stainless hinges. Anglers using smaller chest packs, or anyone who ties particularly bulky foam dries, may find the XL's footprint or slim depth limiting and should consider a deeper or more compact box instead. For anglers who value one large capacity slim box over splitting flies across several smaller boxes, the Kingfisher XL fits that role well.
Frequently asked questions
Is the Kingfisher XL fly box waterproof?
Yes, it uses a rubber gasket seal around the lid to keep it essentially waterproof and to let the box float if dropped.
What are the hinge pins made of?
The lid uses stainless steel hinge pins, which resist rust from repeated exposure to river water better than plain steel.
Will this box fit in a small chest pack?
It may not, since the XL slim design has a larger footprint than standard slim fly boxes to hold more flies, so it is worth checking against your pack's pocket size.
Does the slim depth work for bulky dry flies?
It can compress very bushy or large foam bodied dry flies more than a deeper box would, so anglers who tie bulky patterns may prefer a deeper box.
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