Last year, Cervelo did the test, and the numbers were quite clear: if you’re going to put a standard bottle anywhere on a bike, the best place to put it is between the aerobars, allowing the bottle itself to serve as a cowcatcher, redirecting wind outward and helping prevent it from moving directly back to the open alcove below the chest.

But whither one? We’ve seen janky homemade ones with weak standard cages used to hold a bottle…. well, hopefully, if it doesn’t eject. And once it’s there, where does your Garmin computer go? All that real estate is taken up.

Several brands have come up with some clever designs, created specifically to address the very acute needs of a triathlete placing a water bottle between the aerobars (or more succinctly, BTA); ease of use without affecting aerodynamics.

Now, Inviscid Design has its own: the Speedfil Z4 Cage.

The “Z” in Z4 hearkens to the fact that no baseplate or other fixing apparatus is needed—just four zipties. The Z4 cage features thick, reinforced slotted loops through which zipties are looped and attached to your aerobar extensions. There are a variety of slots, allowing the cage to accommodate a variety of extension shapes and gap widths and cage orientations. The cage will take up any standard diameter water bottles, and will mate with Speedfil’s own A2 refillable bottle/straw setup.


The Z4, with the Garmin clip removed.

 As for Z4 cage material, this is not the place for carbon fiber. Yes carbon fiber lighter and sexier, but given safety concerns (I.e., a reduced chance of a bottle ejecting into your steering path, a more reliable, engineering-ready nylon fiber bottle was Speedfil’s material of choice here.

The clever functional key feature is the use of a clip-on Garmin arm, which mounts to the top of the cage (and is easily removable should the user choose to use the bottle cage in its traditional place. The integrated, clip-attached Garmin attachment, is specifically a recess for the actually retainer clip that is provided to consumers (two are generally provided in fact) when the Garmin is purchased.

Regardless of rearward or forward orientation on the aerobars, the Garmin head is now generally in direct line with the rider’s view, without taking up any added space on the aerobars.

The new Z4 cage, as mounted with the Speedfil A2 bottle.


Among a handful of prototype testers for the last month was Canadian pro triathlete Donna Phelan (who will be publically debuting the Z4 this weekend at Ironman 70.3 Muncie), and a small handful of sponsored Wattie Ink age group triathletes… aaaand this editor. I used it both with the Speedfil A2 bottle locked in place, as well as moving standard bottles in and out during training.

After a month using a few different versions with different levels of cage stiffness or flexibility, ease or stiffness of bottle entry and exit, I must say I kept coming back to the fact that I love the minimal design of the Z4, specifically the lack of a baseplate or any other hardware, using just zipties to affix it to the extensions.

Beyond that, it’s great addressing basic needs. The integrated Garmin mount frees up the extension real estate and places it right in line with the eyes while in the aerobars. Stiffness or flexibility in either of the prototypes we played with was never an issue; the fairly closed-off design of the cage itself is going to keep the bottle where it’s supposed to be. We never had an issue with bottle security in testing. The cage top has a pronounced notch that helps lock the bottle in by the neck. And it was easy-in, easy out, no tight

The only suggestion would be to “lead” the zipties with a few loops of electrical tape around your aerobar extension as a stop. While this may not be a big deal on those with alloy aerobar extensions (as the plastic zipties and roughed alloy surface tend to “grip” one another better), keeping the cage fixed in place horizontally on typically slick, glossy carbon fiber aerobar extensions would be a challenge; a few loops of electrical tape, acting as a “stop” will solve for that, allowing easy in-and-out of bottle swaps during a race.

Just four zipties affix the Z4 to your aerobars.


All told, with just four zipties affixing it to our bike, the Z4 is to our knowledge, and at this point, the lightest dedicated BTA setup with function feature on the market. On heavy tri bikes burdened with enough extra “stuff,” it’s a nice feature… and a rare time that the lowly ziptie becomes a “feature” per se.



Production on the Z4 (and production is wholly done in America) is just ramping up. Key online retailers will have them in stock between the middle end of July, and other local specialty retailers receiving them shortly after.

A look at the ziptie anchors.

Inviscid will be selling the patent-pending Z4 cage (which includes the Garmin arm and zipties) for $40. For those looking to pair the unit with their existing Speedfil A2 bottle, an upgrade version of the Z4 will also include a new new straw clip that allows the straw to lay alongside the bottle and out of a rider’s face while riding, along with a new silicone-backed Velcro fixing strap. That setup will retail at $50.


Still having that Garmin mount location trouble, but prefer to run your own cage and A2 bottle setup (or standard bottle setup)? Inviscid still offers the A2 Garmin Adapter; absent the design-dedicated cage affixment, the slotted Garmin Adapter straps the round mount atop your BTA bottle, holding it taut to the bottle with a Velcro strap with a rubberized inner diameter for firm, flip-free fitment to the bottle. Selling with the new A2 tube clip, it will retail at $20.