In our combined thirteen years of freediving, we’ve gotten pretty resourceful at trying out different brands and types of bifins before committing to buying them. But we realise that’s not possible for everyone.

So, how do you know what freediving fins you should get if you can’t dive-test them beforehand?

Well, this largely depends on what job you want your bifins to do.

If you want a pair of carbon bifins for performance freedive training and competing (in the pool or on the line), that are extremely light and reactive…

… You are going to love the XX Performance Carbon Long Fins by 29/71.

(Need more affordable carbon bifin? Check out the B-Spec Blades for your general training anf recreational needs).

The 29/71 XX carbon bifins for freediving are designed not to cut any corners when it comes to performance, efficiency, and power.

The reason these bifin blades are so good is that they use top-of-the-line carbon fibre, resins, and manufacturing techniques. Of course, this also justifies the price.

More specifically, the internal structure of the XX blades is made from uni-directional carbon fibre, meaning that all the carbon runs in the same direction. Unlike traditional ‘woven’ carbon sheets, this allows the bend of the blades to be very accurately tuned in the manufacturing process and drastically reduces the amount of carbon required. All in all, this produces a more reactive and lighter blade than traditional woven sheets.

The outer layer of the blade, the front and back that we see, is also made with advanced materials, in this case, ‘SpreadTow’ carbon fibre. To avoid going too far into technical terms, basically, this again means that less carbon is used to make the sheets, and therefore the aesthetic part of the blades weighs less and interferes less with the bend.. Again, allowing a lighter and more reactive blade than with standard woven carbon sheets.

See.. No corners are cut in the pursuit of giving us the best bifins possible.

A nifty design plus of all the carbon bifins from 29/71 is that you can easily disassemble the foot pocket from the blade by unscrewing them for ease of packing and travelling. It also means you can swap foot pockets interchangeably with their other range of long and short blades – helping to keep costs down if you want different fins for different activities.

Excitingly they come in iridescent colours Jet Black, Purple, Gold, Titanium, Green and Blue, which really pop underwater, helping you to stand out for safety and Instagramming, of course!

Shop XX Performance Carbon Long Fins by 29/71

Again, just like with the B-spec, this is where things get exciting, and probably the reason you're here reading this...

How do the blades perform in real-life applications?

Obviously, if you’ve read up to this point, you’ll see that I’ve already sprinkled in a lot about how the intended use of these blades is “performance” and right away.. I can say that they don’t disappoint.

The XX carbon bifins really do perform well. Having come from a whole season of using the B-specs (and being extremely happy with them), I wasn’t exactly sure how much better the XX could be.

Well, a few diving sessions in, once I got used to the differences, which include a slightly more tapered bend profile, a softer blade overall, and an extra 10cm of blade to work with.. WOAH! They are super nice.

Here are Nathan's favourite features...

Incredible speed and efficiency with minimum resistance
The first noticeable thing was that they are very soft (my preferred pair are the softest model, the “ultra-softs”), but not in a bad way. Somehow, it feels like wearing short training fins with almost no resistance on your foot, but you're still getting the speed you’d expect from 80cm long fins.

Basically, it tends to feel like your ‘should’ be moving slowly, and then you look at your dive time and realize you're easily cruising at an average of 1.0-1.2m/s. This ‘free’ speed happened effortlessly on 50m line dives (in a lake with 5mm and 1kg), as well as at the end of +2:00 exploration dives in the 25-35m range (in a lake with 5mm and 2kg). I’d expect the same feeling of “free” speed in the sea in my normal 3mm with a 1.5 or 2.5kg set-up.

Of course, the softness of the ultra-softs requires a good awareness and an overall good level of finning technique. You need to be able to “flick” them without overpowering or over-amplitude the blades, especially in the buoyancy zone, but once this is dialled in, the whole dive feels efficient and smooth.

All the power of a stiff blade in a lightweight fin

Unlike other extremely-soft blades that I’ve used, the Ultras seem to get a lot more power when used correctly. Usually, really soft blades just end up collapsing at a certain point, but with the Ultra’s they seem to slightly stiffen up when doing the more sprint-power finswimming style kicking that you might use in a rescue (I tested this by lifting a 16kg bottom weight from 18m in 00:22 seconds).

The reason that I believe they do this is because of the uni-directional fibres.. Even though the blades are very soft, they don’t lose any energy, so the output is really high for the stiffness. That being said, If you are concerned with the fins feeling too soft. Either you’re a bigger guy (+90kg / +1.85m), you tend to wear a lot of weight, are very buoyant, or just generally prefer a more powerful kicking stroke, then there’s always the ‘super-softs’.

Interestingly, Sarah’s preferred fin was the super-soft. She’s lighter than me, wears less weight, and is less buoyant, but in terms of preference, she generally prefers a stiffer fin than I do (in any case, this is good, we got sent one-of-each for testing, so at least we aren’t fighting over the same blades haha).

At least for me, the Super’s are noticeably more powerful, to the point of being certain that no one would need to go any stiffer (soft & medium are available, but I’m certain these stiffnesses are unnecessarily stiff for 99.9% of divers). With the Supers, the first +/-5m is a lot quicker; however, just for my preference of having really soft fins, they just don’t feel as overall efficient for the rest of my dives.

To answer the question, “are the Supers too stiff”? Absolutely not. Watching sarah dive in them and having done two sessions in them myself, they are still on the soft side and very user-friendly for your legs.

So which stiffness would I recommend?

Probably, in most cases, it's going to be a personal preference thing. If you like having slightly stiffer fins, using a more powerful stroke, or are more of a natural strength athlete, then the Supers might be for you.

The Ultras are more suited to divers with really good/smooth technique or if you’re more of a natural endurance athlete. For that ultimate level of efficiency (or maybe “ultra-efficiency” haha), the Ultra’s are probably the best performing.. But you’re still going to do really well with the Supers, compared to most other fins on the market.

Either or, you’ll be plenty efficient, with plenty of power.

Shop XX Performance Carbon Bifins by 29/71

Of course, at £380 ($430) these aren’t the cheapest carbon fins on the market, however for what you're getting with the Super and Ultra Softs, I think they are well worth the price for the level of performance.

Without naming brands, you could pay anywhere from $450 to $750 for bifins with similar performance, which gets absurdly high, and then considering that the XX are softer and more reactive than both of these.. You see the point.

At $430 for the XX carbon bifins, you’re getting top-of-the-line performance for a very reasonable price!

If you’re looking for those ‘next level’ performance bifins and are willing to make a decent investment, the price-per-meter here is extremely good compared to everything else available.

It begs the question, why pay more when you can have so much performance for less?

Shop XX Performance Carbon Long Fins by 29/71