No, it's actually a thermos with the outer layer drilled to allow the gel to fill it and I insert the vials into the container. I had some rubber plugs from god knows what laying around that filled the hole perfectly without problem. The lid to the thermos is an airtight screw on lid. I glue small disc magnets onto the tops which makes retrieving them very easy with a telescoping magnet.
Admittedly the gel (I used Easychill IIRC) reduces the effectiveness of the thermos effect slightly but it does have a few other benefits. For one, the gel has to melt before it drops below 0. Even if it's not frozen completely, it's still frequently colder than 0 degrees (limited to the freezer's lowest temperature of course) and this cools the inner chamber of the thermos reducing the ways for heat to get into the vessel as it hypercools the metal connection to the inner chamber at the lid level (if that makes sense). And finally most importantly, the metal cylinder ensures that if one of the vials were to explode or get broken, the glass would be safely segregated from the rest of the freezer meaning the wife is much more complacent about one of my many "projects." Admittedly I cannot provide evidence that this works any better than using a small cooler but I would think it more efficient and if nothing else it takes up far less space in our freezer. The thermos I have is a promo item I got for free and I can actually comfortably fit 9 of my current vials in it with a small amount of headspace at the top. I guess I could look into filling the container with glycerine which in it's raw form would not freeze (at least in my freezer) barring heavy dilution but it just seems like overkill.