Inviscid Design SpeedFil A2 – Long Term Review

By now it’s pretty obvious that we’re big fans of BTA (between the arms) hydration systems.  If you haven’t read our previous posts regarding hydration options, you can read more about BTA systems here.  Throughout all of our testing, one of our favorite takes on this solution has been the SpeedFil A2.


We first came across the A2 in early 2012. It appeared to be a completely new take on the BTA segment, which has been dominated by Profile Design’s vertical solutions.  The A2 had a striking horizontal orientation and a flexible straw (as opposed to the more common rigid straws).  And on top was the sealable refill port that avoided any splash back.  Overall it seemed to be a completely new take on a BTA system that could more effectively meet the needs of the average triathlete, but did it really work?  Keep reading to find out.

Benefits of the Horizontal BTA

Again, one of the big differentiators of the A2 is its horizontal design, which allows the cyclist to completely hide the bottle from the wind inside their arms.  This works as long as the rider’s hands are positioned in a manner to hide the front of the bottle.  The computational fluid dynamics (CFD) below shows the wind hitting the bottle when the rider’s hands are set too far apart.

CFD Bottle

In order to get the full advantage of the A2 solution a rider should take a fairly aggressive position.  As the CFD demonstrates above, riders with a more open position may find that they require a solution that provides a more aerodynamic face to the wind.

Configurability and Adaptability

While the A2 is a complete hydration system at its core, it’s essentially a very unique bottle top. This provides a great amount of flexibility in the solution—allowing you to create the perfect setup.  The bottle top includes a refill port as well as a hole for the straw.  Everything else in the package is there to help you configure your own distinctive setup.  For example, while the standard package includes a 21-ounce bottle, you are in no way required to use it.  The top uses the standard “Specialized” thread pattern, so you can easily substitute a larger 24-ounce bottle or even an insulated option.  Personally I have gone with the Hydrapak Wooly Mammoth insulated bottle.  The package also comes with a single elbow joint, a few feet of tubing, and a bite valve.  Again, we appreciate the configurability here since you can choose the desired length of straw to match your setup.

The A2 does not come with anything in the way of mounting options (besides some Velcro and zip ties), so you are left to determine what options work best for you. With that said, you can choose to have it pointed toward you or away from you.  Devon uses a Profile Design HC Mount, which works well for him.  I have chosen to use a wider bar setup that cannot fit the HC Mount.  Originally I used a Topeak CageMount based on advice from SpeedFil.  However, upon accidentally damaging my CageMount, (please don’t ask how) I went with a much simpler method—three straps of Velcro—which ended up working pretty well.

The Down-Side of Configurability

Whenever a product is created with configurability in mind there is always the possibility that this can actually lead to a litany of problems.  And unfortunately with the A2, we have found this to be the case.  However, it must be noted that Inviscid’s support staff is truly exceptional and was able to help us through many of these problems.

Because of the location of the straw-port (dead center of the horizontal access), you must use your elbow joint here.  This forces the piping inside the bottle to be raised about one inch from the bottom of the bottle.

Straw Port


The piping does, however, have a natural bend to it. So if you leave 6-7 inches of piping inside the bottle it will inevitably rest at the bottom by the time it gets to the rear of the bottle.  This works just fine as long as your bottle mount has a slight rise at the front (so liquid collects at the rear).  Unfortunately, if you have a slight forward slant (as I do) this means that liquid will collect at the front while the straw is at the back.  To solve this, I was able to get a second elbow joint (SpeedFil rushed one out to me once I had contacted them with my issue and solution) and create a Z-shaped pipe pattern that can pick up the liquid from the front of the

Straw Setuud for a Rise at the Front


Straw Setup for a Rise at the Rear


Another downside of the A2’s configurability has been the tendency for it to leak.  In fact, Devon and I have experienced leaks from different parts of the A2.  I have seen leaks at the bottom of the cap where it threads into the bottle.  As a result, I have found that the bottle’s rubber gasket must be perfectly in place or liquid will seep through.  Alternatively, Devon has found that liquid gets through the straw port and leaks on the front of his bike (something other reviewers have mentioned as well). His solution to this issue involves some rubber cement.

Using the A2

Overall, I have been very impressed with this bottle and have raced with the A2 from Sprints up to 70.3’s.  While it does have the tendency to leak, and it did require some MacGyvering to setup, I ended up with a bottle that I trust on every ride.  The refill port is incredibly easy to use, and I have never had a problem refilling on the fly. I have also had little to no splash-back from the port.

Final Thoughts

In many ways the A2 is what we consider to be a first-generation product.  It’s a great concept but requires a bit of ingenuity to make it work just right for you.  The refill port works perfectly and the product is incredibly configurable.  I have never had any issue recommending the A2 to friends.

Furthermore, the reality is that this is the only horizontal BTA solution currently on the market that can easily be refilled and used.  That is about to change, however. Profile Design’s HC Aero system is nearing final production. And Torhans’ Aero Z system is slated for July.  Based on our conversations with the manufacturers, as well as the product renderings we’ve seen, these products will be slightly less configurable than the A2 but should not suffer from many of the issues we have seen with it. Therefore we should see a number of competitors to the A2 by late 2013. However, the A2 will reign supreme until then.

11 responses to “Inviscid Design SpeedFil A2 – Long Term Review

  1. This is a great review! Thank you! Part of the design concept for the Speedfil A2 was to allow the user vast options for configurability as each athlete has their own cockpit setup. One quick note: to keep the straw from tilting side to side, make sure the straw is not too long but if the straw length is necessary one can use a small amount of medical tape/electrical tape at the base of the elbow joint can increase diameter to tighten the connection.

    • Thats a great tip. I am not sure if you can see in the pictures but on one of our AG bikes we actually used a large rubber band to keep it facing straight up.

      • It’a all about customization for the athlete and that is waht the A2 affords in spades! Also, we are the ONLY BTA option that can remove the straw out of the wind !

  2. My aero bars are close enough that I use two industrial rubber bands to hold my A2 in place. A little user tip, on longer rides and races, I use electrolyte tabs. Because of their size, they need to be snapped in half to fit in the refill opening.

  3. I love the idea of the A2, but unfortunately mine leaks an unacceptable amount, mostly from the refill valve but also from where the straw exits the end of the bottle. My initial email to Speefil was replied to very quickly, and suggested the following three steps to solve the problem:

    1. First, please check to see if you have a black rubber gasket on the underside of the cap? If yes proceed. If no, we will need to send one to you straight away.
    2. If you have gasket in place please be sure that once you have filled/re-filled fluid into the bottle the ball valve is completely rotated to the closed position. (The unit will not move any further).
    3. Be sure you cannot see and visible openings. If this is properly shut, the unit should be almost water tight.

    However, as I had already taken care to ensure that these conditions were met, I asked for any further advice that they could give me, and whether I should try a replacement gasket. Unfortunately, it is more than a week since I sent I sent the email and I am yet to receive a reply. What seemed like good customer service initially has seemingly gone suspiciously quiet when they’re not able to provide a solution to my problems.

    I really want to like my A2, but at the moment it’s just not of an acceptable quality.

    • We have been trying to understand the problem thoughly and therefore looked to replicated the issue. The culprit may be faulty gaskets or a cracked Zerosplash ball valve both of which we can easily remedy and send replacement parts, which we will gladly do. We will follow up with a email to coordinate the replacement part(s).

  4. I purchased my A2 in HK form the official dealer Flying Ball Bike Shop 2 days ago and I noticed upon arriving home (mainland China) that it did not have the bite valve. I went for a ride and as soon as I put a the electrolyte tablet, some “bubbles” increase the pressure and push the liquid up the straw… making it spill all over – in large amounts.
    My solution is to put the tablet in before I refill (leave the refill valve open until there’s no fizziness) and then finish refilling with plain water.
    While I think this may work… I wonder if the bite valve would help to keep the liquid under control.
    I own the large triangular downtube bottle and I absolutely love it.
    I’m hoping the bite valve (I’ll switch it from this bottle) helps… but at the same time, a bit disappointed that the official distributor REMOVED the valve… WTH?
    I read everywhere – even in the printed material – that it comes with it.
    Will test this and report.

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