If you get an El Camino owner, a Dodge Dart or Plymouth Swinger owner, and a Ferrari 308GTS owner together and crammed them into a damp tent, what do you think they could all find in common to bond over? The difficulties of trusting people’s intentions when you’re wealthy? The best way to drag a Jetski into a truck bed? How to best remove vomit from vinyl seats? No. None of these. There’s only one like point of commonality, and it’s worth taking note of, which is why we’re here.

That one thing? The back window on all these cars. Yes, there really couldn’t be a set of cars more different (well, they’re all RWD, I guess) and yet they all share something wildly uncommon in automotive design: a concave rear window.

Yes, the concave rear window is a sort of unappreciated bit of automotive design that is all but extinct now—in fact, I can only think of one modern car that has anything remotely like this today: .

Even that Prius small-of-the-back-type window isn’t really what these concave rear windows were like; the concave rear window used by Mopars, El Caminos, and Ferrari 308s, and other makes like Citroën was really kind of a lovely, sculptural object, a bit of curved glass that doesn’t exactly make a lot of sense, rationally.

Really, concave glass is the exact opposite of what most automotive glass strove to be when it really wanted to show off, which was convex.

Most automotive glass that was featured as a styling element tended to be big, cavernous wraparound windshields or crystal bubbles at the rear, panoramic glass that expanded the space inside the car.

Concave glass, did the opposite: it pushed inward, recoiling from the outside world, and actually reduced the interior volume of the car.

It generally didn’t make too much sense, but it had a strange appeal.

It could make a car like a Plymouth Swinger look sort of lean and hungry, a nice change from the bloated cars of past eras. A flat rear window wouldn’t have changed the look of the Dart/Swinger that much, but the concave glass adds so much more unexpected character, especially with how it turns the meeting point of the roof to the body into a graceful arc.

Weirdly, the El Camino and the Ferrari 308 GTS actually use their very similarly-shaped rear windows to accomplish the same thing: to fill the area between buttressing B-pillars in a way that’s more exciting than a flat, narrow piece of glass.

These two very different cars found themselves with the same basic design problem to solve, and arrived at the same solution. They could have used flat glass and some side panels where the glass edge met the side buttresses, but that just doesn’t have the same refined feeling as the inwardly-curved glass.

The concave glass ties the buttresses together with the roof and rear deck (or bed) of the car in a way that flat glass and side panels never could. It’s an unexpected elegance on the El Camino, and the right bit of detailing on the Ferrari.

It’s simple, unexpected, subtle, but just finishes each of these cars in a really beautiful way.

So, take a moment and appreciate this little detail, a panel of bent glass, an automotive styling detail that was never popular, and likely won’t ever be. It’s about as sculptural as glass gets in mass-produced cars, especially considering the era.

I’ve always really loved these sorts of windows; take a moment the next time you see one, and, if it’s okay with everyone, run your finger along that inner curve. It’s weirdly satisfying.

(thanks for reminding me of this, Hans!)