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Rain Shell Review: Lightweight Black Diamond Climbing Jacket Punches Above Its Weight Class

Black Diamond Fine Line Rain Shell

Black Diamond’s new for 2018 BD.dry produces an excellent three-season, just-in-case rain shell.

Black Diamond Equipment introduced its own waterproof-breathable concept for apparel in the spring of 2018. Dubbed “BD.dry,” the tech finds its way into a minimalist rain shell called the FineLine Stretch. We’ve been testing the BD.dry-equipped shell since March in both urban and wilderness environments.

In short: As the name implies, the FineLine Stretch Rain Shell is a two-way-stretch, extremely light (verified 8 ounces for size M), compressible rain shell. Available in women’s and men’s, it performs excellently as a just-in-case windproof, waterproof-breathable outer layer. It works best for three-season rock climbing, backpacking, and aerobic sports. It’s not the lightest rain shell on the market, but the excellent mobility and price ($129) make it a top choice for that one jacket that never leaves the pack.

Black Diamond Waterproof Membrane: BD.dry

Black Diamond Fine Line Rain Shell

Black Diamond Equipment positions BD.dry as a concept on non-Gore-Tex, waterproof-breathable materials. And it’s not tied to a single fabric or garment. For example, BD.dry works in the two-way-stretch FineLine, but it’s also in the Black Diamond Recon Stretch Ski Shell, which uses a different three-layer, four-way-stretch material that has higher water resistance and breathability ratings.

The FineLine Stretch Rain Shell uses a patented PU membrane with a stretch-woven nylon face fabric from Toray. Black Diamond guarantees the fully seam-taped, 2.5-layer membrane to withstand a 10,000-mm water column while providing a vapor transfer rate of 10,000 g/m²/24 hours.

Practically speaking, the FineLine Stretch will withstand drizzle, mist, and light rain or snow. This jacket is not designed for heavy or soaking rain.

Visual Inspection and Fit

Close inspection of the FineLine Stretch Rain Shell reveals clean overall construction. All seams are tight and evenly stitched, seam allowances are narrow, the PU membrane feels smoothly laminated throughout, and the seam tape is symmetric with no loose edges or wrinkles.

Black Diamond Fine Line Rain Shell

The main zipper is a reverse-coil, PU-coated, waterproof YKK. The generous hood has a single elastic cord and toggle adjuster, as does the lower hem. Partial elastic along the wrist openings helps keep a close fit, and small necessities have a place in one vertical, zip-up chest pocket.

The men’s FineLine Stretch Rain Shell’s cut is definitely on the slim side. I’m 6 feet tall and 167 pounds, and the jacket allows a base layer and a thin puffy only. It’s cut long in the torso to reach well below a climbing harness waist belt, the sleeve length is generous, and there are underarm gussets. The FineLine Stretch Rain Shell is also available in a women’s version.

Black Diamond FineLine Stretch Review: Rain Shell

I tested the Black Diamond Equipment FineLine Stretch Rain Shell in both the city and at local crags. At a week-long conference in Minneapolis in May, where it rained every day on my pedestrian commute, I pushed the limits of the BD.dry’s breathability.

Black Diamond Fine Line Rain Shell

Warm temperatures combined with high humidity produced condensation underneath my backpack, but otherwise vapor escaped during the nominal output of walking. Jogging under the same conditions proved too much, however, and my tech T-shirt underneath was damp after a few minutes. There are no venting options other than the main zipper, a trade-off for the minimalist design and weight.

I packed the FineLine Stretch Rain Shell on every trip during the spring season to the local crags. Its extreme compressibility and low weight made it almost nonexistent in my pack.

As for performance, the jacket never failed to keep my base layer dry during unexpected spring showers. The DWR treatment functioned remarkably well for a lightweight piece, beading water and letting it roll off freely and I never noticed a wetted-out area, even under pack straps. Plus, the FineLine demonstrated impressive wind resistance given its light weight and would be adequate for shoulder season use.

Unfortunately, with no adjustable wrist closures, water would drip in from the backs of my hands, another concession for weight. And, like other rain shells without a drop liner, the inner membrane felt cold against the skin when the temperatures dropped.

Black Diamond FineLine Stretch Review: Climbing Shell

Where the FineLine Stretch Rain Shell excelled was mobility when climbing. The lack of hand pockets and slim torso dimensions provided a great fit under the climbing harness. After I reached my arms overhead to “set” the jacket before leaving the ground, the shell went mostly unnoticed the rest of the climb.

The underarm gussets and sleeve length rarely left my wrists bare, and the two-way stretch provided just enough elasticity for unhindered twisting during steep climbing. Meanwhile the hood, for such a light shell, provided outstanding fit and function when worn over a climbing helmet. And its single elastic cord adjuster kept it secured to the helmet, maintaining peripheral vision during head pivots.

Plus, the FineLine Stretch Rain Shell also packs into its chest pocket, producing a 7 x 7 x 1.5-inch package that clips to the harness.

The shell showed no signs of weakness during three straight months of testing. Overall, the FineLine’s durability proved excellent for a garment of its weight. In addition to being a three-season emergency layer, it’s also durable enough for regular use during backpacking, rock climbing, and aerobic sports.


The FineLine Stretch Rain Shell just replaced my longtime “always-packed” shell (Outdoor Research Helium II). Although I’m paying a slight weight penalty for the switch, the improved mobility and climbing performance (hood and under the harness fit) won me over.

The overall performance, for a tiny 8-ounce package, is striking, especially considering this is Black Diamond’s first proprietary waterproof-breathable effort. For activities short of alpine, the Black Diamond Equipment FineLine Stretch makes a stellar just-in-case rain shell.

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