Specialized Therminal Alpha Jacket and Deflect H20 Mountain Jacket Review – by Greg

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Race day is always wrought with varying degrees of anxiety.  How many calories do I carry?  Did I set up the right tires?  Do I carry an extra tube?  Have I put the miles in to meet my goals?  So much time and preparation leading to a single day event can really tax the mind. Racing in the dead of winter adds an additional layer of dread to my planning and preparation.   For me, race day success starts with having my clothing dialed.  Enter the Therminal Alpha Jacket ($200) from Specialized.  Having the chance for a few test rides leading up to my race in mid-February, knew I was in good hands.

We at Fat-Bike.com don’t just ride around the block and drop a few words about the products we get to test.  We like to really give products the one-two punch.  While I have taken this (and the Deflect H20 Jacket) for a few shorter rides, I knew a four-hour fat bike race was just the ticket for the Therminal Jacket’s first big test.  For the unfamiliar, The Polar Roll is a 30-mile fat tire race from in Marquette to Ishpeming, Michigan offering a challenging and fun racecourse.  While they call it a 30-mile race, the actual course file is 38.76 miles according to my Strava feed.

The extra 8.78 miles was a little gift from the Polar Roll crew, kind of like that onion ring that sneaks in with the French Fries.  Temperatures were forecasted in the single digits for the 8:00 AM start with a feisty 15 mph headwind to keep us company for the majority of the point to point course. I layered with a wind stopper t-shirt, a merino long sleeve jersey, and then the Therminal Jacket.  Since I fly the THC flag, I topped off the kit with my Team Hollywood Cycles wind vest.  My high-vis Bell helmet tied the kit together nicely if I may say so.


Now that I’ve set the stage, let’s take a closer look at the Therminal Jacket.  What struck me out of the box was the jacket’s weight and compactness.  It comes in at a whispy 138 grams and takes up very little space in a pack making it an ideal companion for bikepacking and adventuring.  Designed as a mid-layer, it is form-fitting.  It doesn’t have the stowable feature of the Deflect Jacket with SWAT (that I will feature in another writeup), but it still packs down pretty well and is lighter than a protein bar.  One of the unique features of this jacket is the material construction.  The smooth Woven Pertex® Quantum Air outer-shell is tough enough to take some branches, while the interior’s Polartec Alpha® breathable insulation creates a super breathable, lightweight, and warm garment. 

The jacket is available in Black, Hyper (tested), and Oak Green.  There are two zippered hand pockets on the front and an uninsulated hood for extra weather protection.  Adding a hood without the bulk of the Polartec material is smart for keeping you warm without overheating under load.  You can pop the hood up under your helmet without compromising fit and comfort.  Other features include roomy arm length, which I always appreciate, reflective accents to alert those masochistic motorists, and a high collar to keep the wind and cold at bay. Specialized recommends sizing up if you want a looser, street style fit.  The only missing feature for me is a rear pocket to stash a bottle, tube or whatever you might need.  In my world, cycling jerseys and jackets without a rear pocket is a no-no. 

To note, this is not a shell, so it lacks water repellency like a DWR finish and Windstopper material.   Specialized recommends wearing the Alpha Therminal as a mid-layer jacket under a shell-like their Deflect H20 Mountain Jacket ($225).  Since I like to live fast and loose, I topped off my race-day kit with a wind vest and found the combination to be perfect for the day’s conditions.  For non-race conditions where lower watts and tempo heart rate are the norms, a light jacket like the Deflect H20 Mountain is a great choice.  Let’s take a look.

I’m always a little skeptical about mountain bike garments for rainy days.  After all, if we are serious about maintaining the hard work put in by the trail angels, we need to stay off the trails when it’s wet and rainy.  Specialized notes this in the description on their web site, but I wanted to plug that ethos again for those of you that still think it is cool to get your bike all muddy by riding trails in the rain.  Thank you Specialized for the reminder.

The Deflect H20 Mountain Jacket comes in Oak Green and Black (tested).  Regular retail is $225, but you can pick this up on closeout for $119 while supplies last at Specialized.com.  I really like the fit of this jacket.  The body has a comfortable loose cut, not too tight, allowing for a mid-layer to compliment the weather protection offered by the 3-layer stretch fabric. Specialized does not boast this jacket to be waterproof, but as the name suggests, it does feature sealed seams, watertight AquaGuard®  zippers, and adjustable wrist seals to ward off any water intrusion. This garment is lightweight and packable so you can stow this away in your pack if you find yourself in on the wrong side of the rain clouds.  Additional features include:

  • Suede zipper shield to protect your chin from abrasion.
  • One zippered chest pocket for small items.
  • A hood with a rain visor and adjustable drawcord to fend off the drips
  • High-visibility reflective elements to warn drivers of your presence after dark.
  • Deflect™ UV 50+ protects your skin from harmful ultraviolet rays.

The final feature to talk about is the Bluesign® approved fabric.  Bluesign® was a new term to me, so I had to poke around the inter-webs to find out more.  I was happy to see that Bluesign® refers to a manufacturing gold standard for sustainable, healthy, and environmentally responsible workplaces for garment manufacturing. Serving as an independent accreditor, Bluesign traces each textile’s path along the manufacturing process, making improvements at every stage from the factory floor to the finished product.  I think that’s pretty cool. 

This week we’ve seen some elevated temperatures here in the Upper Midwest, but it has been cold enough to warrant a layered approach for comfortable riding.  Following the advice from Specialized, I layered the Therminal jacket with the Deflect H20 Jacket.  The fit was just right.  I didn’t feel like the Stay-Puff Marshmellow Man.  I had plenty of protection from the wind and cold without the bulk. The Deflect H20 is designed for wet conditions, so check back later this season for an update on how it holds up under a spring rain.

I like to offer some critical comments, but I’m struggling to find anything too serious.  I mentioned the lack of a rear pocket on the Therminal, and that holds true for the Deflect jacket as well.  The Lord Vader black looks good, the seams and stitching are solid and familiar with the quality of Specialized gear, I am confident this one will survive many seasons ahead.  To conclude, I really like the Therminal Alpha as a mid-layer and give the Deflect H20 Mountain Jacket a double thumbs up for price and quality. 

About Gomez 2576 Articles
Just an old cat that rides bikes, herds pixels, ropes gnomes and sometimes writes stories. I love a good story.


  1. Nice review Greg. On the Thermal Alpha Jacket, is the insulation continuous throughout the interior of the jacket or is it just in specific areas?

    It’s going to be interesting in the next few season to see what is done with these new generation “Active” insulators like Polartec Alpha.


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