Ride through a Belgian summer.

While we're all familiar with the expression of racing in through a "Belgian summer," the reality of this expression is often lost on the uninitiated. However, even the toughest of cyclists are known to be harboring unseen, secret advantages. However, we're not talking about embrocation, after all, you can smell a Belgian peloton approaching from a kilometer away. No, we're talking about the kind of wind-blocking protection that's derivative of Castelli's Flanders Wind Base Layer.

To start, the Flanders base layer features multiple fabrics in multiple locations. In other words, Castelli was dedicated to applying the right tool for the job. At the body, the base layer uses a multi-denier (multi-weight) polyester composition. This material was created with a rib-knit, 3D structure that enhances mechanical moisture wicking, while also creating a stretchable, conforming fit around the torso. However, it's important to note that this design essentially creates channels that keep the fabric largely off of your skin. Ultimately, this reduces, if not eliminates, the threat of abrasion.

And, to fulfill its namesake, this base layer features a membrane of Gore's patented WindStopper. This material is completely windproof, which cuts out most of autumn's chill. So, as Castelli puts it, you're able to look tough from the outside but stay comfortable inside.

At the underarms, a natural evacuation point for excess core heat exhaust, Castelli placed a perforated mesh polyester. And, as you probably guessed, perforation equates to ventilation. As a result, your body temperature remains well-regulated, which prevents the threat of overheating. For the sleeves, Castelli retained the lightweight polyester theme of the base layer, only the fabric used here features a four-way stretch. This way, you're guaranteed an uncompromising freedom of movement.

Further along with the construction, you'll find that Castelli only used four-needle flatlock stitching throughout. This construction method equates to a lower-profile seam and a flat stitch. And, as a result, the base layer lays closer to the body, which makes for increased moisture management and no chafing. Lastly, Castelli sought to ensure that your body obtains total coverage, and to do so, it incorporated a crew neck and an flat finished, elongated back.

The Castelli Flanders Wind Base Layer is available in the color White and in five sizes from X-Small to XX-Large. Please note that Castelli recommends this base layer for a temperature range of 57 to 68 degrees Fahrenheit.

  • Reviews
  • Q & A

My favorite base layer

  • Familiarity: I've used it several times
  • Fit: True to size
  • Size Bought: XL

I originally bought one to try out - I now own five. The recommended temp range is 57-68 degrees, and that is pretty much spot on with just a short sleeve jersey.....and also arm warmers if it's below 65 and/or windy/cloudy. I haven't had to ride in temps below 57 yet (yay SoCal), but for high 40's/low 50's, I would throw on a vest in addition to this base layer.....which beats wearing a jacket. The material itself feels a little flimsy, so let's hope it holds up.....but other than that, they knocked it out of the park with this shirt.

One my favorite layering pieces!

  • Familiarity: I've put it through the wringer
  • Fit: True to size
  • Size Bought: Small

Runs true to Castelli size. I wear a small in Castelli jerseys, jackets and shorts, and this one fits perfectly as a small.

I use this as a layer underneath my alpha jacket during the winter. I use it as a layer underneath my summer jersey in the fall and late spring, which the wind block obviates the need for a vest. It breaths so well since the wind block is only in the front.

It's my most used layering piece. Since I ride 6 times a week, I have six of these.

Performs great...quality is so-so

  • Familiarity: I've put it through the wringer

Owned this base layer for over a year now. It performs great and really keeps you warm under a jersey when the temps dip down low. The biggest problem I see is the overall material quality and construction. The mesh under the arms is very fragile and has torn numerous times. In addition, the stitching seems poorly done and the workmanship was so-so. I've had to manually fix the stitching in 3 different places along the front panel where the windproof membrane is attached to the rest of the garment. I expected more out of Castelli, but this one is not made in Italy either.

Miracle for micro-climates

  • Familiarity: I've used it several times

I have ridden 3 times now using this new base layer in the SF Bay Area. Super happy. On a grey windy day, with a thin long sleeve added, it kept me comfy. On a sunny day alone with a jersey, I was able to remove the arm warmers but survive the downhill blast. It shields, it wicks, it dries, it fits! It's a go-to keeper for riding through all the micro-climates I face heading out of the city and across the GG bridge into wind, shade and sun