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 which 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.
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 actual retainer clip that is provided to consumers 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.