New Simms G4 Fly Fishing Jacket | Under the Hood

With Winter right around the corner, anglers across the country have a lot to look forward to as it happens to be one of the fishiest times of the year — as well as one of the rainiest. In order to capitalize on all of the opportunities that come with Winter, a quality rain jacket is worth its weight in gold. Designed and developed to deliver next-level waterproof/breathable weather protection, comfort, and durability — the all-new, award-winning G4 Pro Jacket ranks as the most technologically advanced, performance driven rain jacket Simms has ever released.

A Brief History

The all-new G4 Pro Jacket has evolved from a long lineage of technical outerwear. Its origin dates back to 1994 when Simms introduced the Dry Coat, the first piece of outerwear Simms released equipped with Gore-Tex immersion technology. 

Simms G4 Fly Fishing Jacket

      From Left to Right: Paul Dubas, Bob Krumm, and Mike Craig pose for the original Dry Coat Ad shot by Andy Anderson at the Drive-In on Montana's famed Bighorn River.

The Dry Coat hit the market right on the heels of the first waterproof/breathable wader that Simms introduced in 1993. Like the wader, the Dry Coat was a true gamechanger and served as the baseline for other Simms outerwear favorites such as the Guide Jacket and G3 Guide Jacket. The original G4 Pro Jacket landed with specialty retailers in 2008 and since then, the jacket has gone through several wildly popular iterations.  

Historically, in addition to utilizing premium Gore-Tex waterproof/breathable fabrics, a key selling point of the G4 Pro Jacket was to provide anglers with ample and convenient onbody storage. This way, in lieu of a pack or a vest, anglers could simply stash all of their gear inside their jacket and keep it within easy reach. To accomplish this, in the past, the G4 Pro Jacket implemented several different pocket configurations. At one point, Simms’ flagship rain jacket’s pocket array included nine different pockets: Two traditional baffled chest pockets, two handwarmer pockets, two hidden rear “game pockets”, a zippered stash pocket on the sleeve, and two internal dump pockets. This configuration did in fact provide a lot of storage but over time, the design team at Simms began to devise ways to rebuild the jacket with a much more sleek and streamlined appearance without sacrificing its renown onbody storage.


Before getting into the new G4 Pro Jacket’s pocket configuration and features, we’ll start with the main engine behind the performance aspect of the piece — the fabric. Since it initially dropped, Simms utilized Gore-Tex fabric in the G4 Pro Jacket and the same is true for the latest iteration. Specifically, the jacket is powered by a 3-layer Gore-Tex Pro Shell. Pro Shell is the highest performing fabric in the Gore-Tex portfolio. In short, it offers performative advantages across the board and boasts outstanding durability. Pro Shell is lightweight but extremely tough in terms of puncture and tear resistance as well as abrasion. It’s also a very supple fabric which goes a long way towards comfort and range-of-motion. And of course, in addition to being waterproof, it also breathes extremely well. 

Simms G4 Fly Fishing Jacket


Inclusive of Simms’ tried and true 3-panel, 3-point adjustable storm hood, the latest version does not include the old internal collar. Omitting this feature removed a sizeable amount of weight and also simplified the design — truth be told, this feature was more or less unnecessary and got in the way, especially if the hood wasn’t in use. The jacket opens and closes with a highly water-resistant center-front zipper that’s backed by what the product team refers to as a rain gutter. This ensures that even if driving rain was to penetrate the jacket, the rain gutter is yet another line of defense to prevent moisture/rain from reaching interior layers of clothing.

Simms G4 Fly Fishing Jacket    The new G4 Pro features a 3-panel, 3-point adjustable hood for maximum weather protection. 

Moving on to the front of the jacket and the pocket array — for any fans of the old Slick Jacket, rest assured, many of the new design/feature cues found in the new G4 Pro Jacket came directly from the old West Coast Steelheader standby. As previously mentioned, Simms aimed to maintain the storage aspect of the jacket but wanted to do so in a way that allowed for a streamlined front.

So, instead of two oversized, top load baffled chest pockets, the design team implemented two oversized vertical entrance chest pockets with water-resistant zippers and bonded welts for extra protection from the elements. This design (borrowed from the old Slick Jacket) is what provides the sleek and streamlined front. The pockets themselves are huge. They can each easily accommodate large fly boxes and they also feature internal stretch woven dump pockets to keep specific gear in specific places. The left pocket also includes a tethered sunglass chamois. 

Simms G4 Fly Fishing Jacket

      The G4 Pro Jacket features a sleek and streamlined front without sacrificing on-body storage. 

The jacket also incorporates two zippered micro-fleece lined handwarmer pockets. Another very cool feature taken from the old Slick Jacket lives inside these pockets. When you reach inside, you’ll feel another zipper on the inside of each pocket. When you unzip these zippers, you now have access to the upper portion of your wader without having to take off, or unzip your jacket. It’s a small detail that makes all the sense in the world when it’s raining and the bite is on.

Simms G4 Fly Fishing Jacket

Microfleece lined handwarmer pockets thaw frozen fingers. These pockets also incorporate an internal zipper that give anglers access to the upper portion of their wader without having to take off or unzip the jacket.  

Finally, on the interior of the jacket, there’s one more zippered stash pocket, perfectly sized to house a set of keys, a couple tippet spools, or a phone. It’s also important to note that with the exception of the interior pocket, all of the pockets feature highly-water resistant zippers. In addition, if a zipper isn’t fully closed and rain gets inside, or water gets in from a deep wade, the pockets also come equipped with drain holes.

Once again, range-of-motion is something Simms doesn’t take lightly and therefore, the sleeves of the G4 Pro Jacket are articulated. Simms has also modified the cuff design by incorporating a small, pliable piece of Toray that’s overlaid with an adjustable Velcro closure. In combination, this material and the closure allow anglers to essentially create a watertight seal to prevent rain or water from making its way into the sleeves of any underlayers.

Simms G4 Fly Fishing Jacket

     Articulated sleeve allow plenty of mobility for casting, rowing, and fighting fish.

The jacket also includes a revamp of the old tuckaway loop fly field. This feature now lives on the upper left chest portion of the jacket and is much smaller than the previous version. Flip it out and stash unproductive flies or keep a few on-deck options at the ready. When not in use, simply tuck it away.

For deeper wading missions, the jacket is cut slightly longer than traditional wading jackets and also features an adjustable bottom hem to keep water out.

Since its inception, Simms’ G4 Pro Jacket has enabled countless anglers who would otherwise have been forced to head for cover to remain in the elements indefinitely in pursuit of one more cast. The latest iteration is no exception — in fact, it’s a great example of utilizing aspects that have worked in the past and eliminating aspects that haven’t. It’s also inclusive of new innovations and advancements that make this version the best G4 Pro Jacket Simms has ever released. 

Simms G4 Fly Fishing Jacket

Reproduced courtesy of Simms Fishing Company: The original article can be found here: