Castelli Pro Issue Base Layer review – lightweight summer brilliance

Good looks and great wicking from a superlight base

Man wearing white summer base layer T-shirt outside
(Image: © Sean Fishpool)

Bike Perfect Verdict

It’s only a base layer, and a pricey one at that, but it’s a stealth weapon for keeping clamminess at bay.


  • +

    Really light and unobtrusive

  • +

    Wicks well

  • +

    Looks good


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    Size up to get the fit right

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    No antibacterial treatment

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    High price

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Part of me apologises for the predictability of giving editor’s pick in our best cycling base layers for summer guide to a $/£50 base layer, especially as it’s from a brand with a well-known focus on fit and performance. But if I had to keep just one, it’d be the Castelli Pro Issue, for its comfortable, unobtrusive fit, good looks, and ability to keep clamminess at bay.

It was a hard decision when I tried to decide by reason alone, so I went with gut feeling. In our best cycling base layer buyer’s guide we had a couple of pure mesh options (brilliant at staying dry, not so soft), a couple of flatter, silkier options (superlight, a bit wetter), and a majority of ‘filled mesh’ options, like the Pro Issue, where the mesh is filled with filament-thin fabric where the holes would be.

These often hit a sweet spot of breathability, wicking and comfort, and the Pro Issue did this particularly well.

Man wearing white summer base layer T-shirt outside

The fit of the Pro Issue is snug and nicely long (Image credit: Sean Fishpool)

Design and specifications

The fit of the Pro Issue is snug and nicely long; I found Castelli’s size guide pretty much bang on (a small for a 36in chest is close all over but not constrictive). The diagonally-seamed shoulders make for easy articulation and a nice rounded fit. And it’s very much made for wearing under snug jerseys, if you want to, with a fairly close fit around the armpits and extra-short sleeves, alongside the overall close fit. (There’s also a sleeveless version.)

To maximise breathability and wicking, the Pro Issue is made from a checkerboard pattern of polyester wicking fibres, in which the thinner squares are almost transparent – Castelli calls this ‘3D mesh’. There’s a nice amount of stretch to the fabric, meaning it’s going to stay in contact with your skin no matter what moves you’re making.

Man wearing white summer base layer T-shirt outside

The ‘3D mesh’ hits a sweet spot between full mesh and a flat weave (Image credit: Sean Fishpool)


I liked the way the Pro Issue just feels like it’s there waiting to unobtrusively get on with its job. It fits under anything, and it doesn’t feel like a compromise or a big decision to be wearing it. I can see why sleeveless base layers are appealing, but this fitted so nicely for me under a jersey that I preferred it, frankly, for keeping the armpit sweat off my jersey.

Even the best base layers aren’t magic – they do get wet as they work, of course, and your skin will have a glaze of sweat on it,  but it feels dry while it all happens. You have to put your hand on the Pro Issue to realise it’s damp, and it just doesn’t stick to the skin like a wet jersey. This is largely to do with the fabric, but also the fit. 

If it was super-hot (by UK standards!) – above 25C/77F, say – I’d choose a pure mesh base like the Brynje Super Micro T-shirt or Castelli’s Core Mesh over a filled mesh like this; (or go without a base if I was happy to live with a damp jersey against the skin for the sake of cooling), but for most summer riding, this is a smashing all-rounder.


Pure mesh bases may keep you even drier, others may be more sophisticated, and many are cheaper, but the Castelli Pro Issue is a very easy summer base layer to reach for. If you’re not the kind of person who’d normally wear a base layer but you’d like something to stop your jersey feeling clammy, this is a great – if expensive – place to start.

Tech specs: Castelli Pro Issue Base Layer 

  • Price: $59.99 / £48.00 / €44.95
  • Weight: 54g (small)
  • Sizes: Men XS-XXL, Women’s XS-XL
  • Colors: White
  • Key materials: 100% polyester
Sean Fishpool
Freelance writer

Sean has old school cycle touring in his blood, with a coast to coast USA ride and a number of month-long European tours in his very relaxed palmares. Also an enthusiastic midpack club cyclocross and XC racer, he loves his role as a junior cycle coach on the Kent/Sussex borders, and likes to squeeze in a one-day unsupported 100-miler on the South Downs Way at least once a year. Triathlon and adventure racing fit into his meandering cycling past, as does clattering around the Peak District on a rigid Stumpjumper back in the day.

Height: 173cm

Weight: 65kg

Rides: Specialized Chisel Comp; Canyon Inflite CF SLX; Canyon Aeroad; Roberts custom road bike