The kids are going to be alright. They love classic cars and more than 1/4 are learning to work on one themselves. Optimism is the general consensus of Hagerty’s annual “Future of Driving” survey. But one interesting tidbit stood out. The most common classic that Millennials explored insuring wasn’t some muscle car from the 1960s or a Jeep from the 1970s. It’s General Motors’ GMT400 generation of trucks and SUVs, originally sold from 1988 through 2000.

Are GMT400 trucks collectible? In just three years I’ve watched this question go from having almost no Google searches to surging popularity. Today, over 10,000 folks are entering some variation of GMT400 in Google every month.

“GMT400” is a broad term. It stands for the “General Motors Truck platform” used from 1988 through 2000 (technically produced until 2002 in some markets). It includes the Chevrolet and GMC pickup trucks (the C/K series) and SUVs such as the Chevrolet Suburban, Chevy Tahoe, and GMC Sierra. And it’s controversial.

I come from a small, rural town. Many folks are still using trucks from the 1990s as their work vehicles. If they own a newer truck, they may still run a GMT400 when the roads are salted as their “winter beater” because they don’t care if it gets rusty. Few folks there–young or old–consider these “classics.”

When Hagerty interviewed Gen-Z (born 1997-2012) and Millennial (born 1981-96) drivers, they found almost a third consider themselves collectors who have owned or currently own a classic. (That’s 30% of Millennials and 32% of Gen-Zers). The analysts also found most of these enthusiasts discovered their passion at an in-person car show, though they now use social media to connect to other collectors. They are into a wide variety of vehicles form the past four decades.

Hagerty also looked through its classic car insurance data. It found that the most common classic Gen-Z drivers inquired about insuring was a 1990-1998 Mazda Miata. That’s the first “NA” generation with the flip-up lights. So what about Millennial drivers? Their favorite was the GMT400 era trucks and SUVs.

Of the young respondents interested in classic vehicles, 38% say it is SUVs they love most. Sedans got 26% and trucks came in third with 19%. Gen-Z is interesting in that 23% are intrigued by classic luxury cars.

So what’s going on here? Obviously, as every generation of car collectors comes of age, they christen a newer generation of vehicles “classic.” I expect many Millennials had a GMT400 era Suburban or Sierra in the family–or even just saw one around the neighborhood–and it made an impression. The GMT400 era trucks and SUVs featured comparatively retro looks into the late 1990s. So they may be a popular project vehicle because you can find a two-tone, vintage-looking truck with a full OBD-II system (1996 and later).

There’s also certain vehicles enthusiasts buy at certain stages of life. A roadster, such as a Miata, has always been a popular enthusiast car with younger folks who don’t yet need a back seat for all their dogs and babies. A classic truck is often more appealing as a third vehicle, something to take to Home Depot after you’ve bought your first home.

So in this way, the model year of “classics” that Gen-Z and Millennials love may be surprising. But the vehicles themselves are timeless.