Today is Cassette Store Day, Burger Records’ annual tape-centric answer to Record Store Day. This year’s exclusive releases include Jay Reatard’s Blood Visions, that dog.’s Old LP, Dr Dog’s Midi Swamp, and a bunch of ska compilations. But Popular Mechanics reports that there’s a worldwide materials shortage putting a damper on the festivities.

Although the cassette resurgence hasn’t quite caught up to the vinyl revival, the format saw a 136% rise in sales in 2017 and a 19% increase in 2018, with 118,200 tapes sold in the US last year. But production has slowed to a crawl this year due to a shortage of gamma ferric oxide, the most common material used to make magnetic tape.

According to a letter from the National Audio Company (NAC), the largest audio cassette tape manufacturer in the United State, shared on Twitter by the small Chicago electronic label Hausu Mountain, the only factory in America that refines high-grade gamma ferric oxide has been undergoing renovations to refurbish its aging machinery. Naturally, that means there’s a lot less gamma ferric oxide to go around.

There is some “light at the end of the tunnel,” according to NAC owner Steve Stepp. Although they’re still waiting on 50 tons of gamma ferric oxide from their supplier in Minnesota, they have recently acquired 11 tons of the stuff. “But it’s not a train, it’s trucks from Minnesota,” says Stepp. So yeah — if you’re old school like that, you’d better stock up on those cassettes while you still can.

Some of the cassette manufacturing people that I've talked to about this haven't gotten this letter. I think it's probably good for all to see.

SIRI. ALEXA. LEXA. How do I mine high grade gamma ferric oxide from the earth? LEXA! Ferric oxide! with Gamma? PRECIOUS METALS!? SIRI! pic.twitter.com/rCeAImJQqh

— Hausu Mountain (@HausuMountain) October 9, 2019