Hungry? Fruity Pebbles cereal is accepting rocks as payment at these Walmarts

The retailer is offering a box of Fruity Pebbles or Cocoa Pebbles cereal to shoppers in exchange for … well, pebbles. In fact, any sort of rock or stone will be accepted in exchange for the childhood staple. And it doesn't matter if you've got a handful of rocks or just one.

The traveling promotion kicks off on Sept. 8 and will make four stops – one at the company headquarters and the others at towns that have the word "Rock" in its name. Specifically, Rock Hill, SC will be the first to take advantage of the deal on Sept. 8. From there, Little Rock, Ark. will get its chance on Sept. 12. Bentonville, Ark. can exchange its rocks on Sept. 14 and Round Rock, Texas will offer the deal on Sept. 17.

Only one Walmart in each city will honor the barter.

“The Pebbles cereal brand is all about inspiring unexpected joy and a break from everyday routine,” said Ali Shater, Pebbles senior brand manager, in a statement. “We’re inviting fans to embrace a little absurdity and walk away with something fun and familiar."

The rocks will be donated to local parks and recreation departments, Walmart says. You'll have to be 18 or older to get the free box.

 The promotion comes as the cereal market heats up, but also faces political pressures. In July, Ferrero Group and WK Kellogg $K Co announced a $3 billion deal that saw the breakfast food brand folded into the corporate parent of such brands as Nutella, Tic Tac, Butterfinger, Baby Ruth, Famous Amos, and Bomb Pops.

Cereal makers, especially those that have many brands aimed at children, have been the target of HHS Secretary Robert F. Kennedy, Jr., who has banned eight commonly used artificial food dyes.