Once again, Lucky Charms is coming out with boxes of nothing but the marshmallows. The all-marshmallow variety first appeared for a 2015 sweepstakes, and later resurrected for a 2017 promotion. This time around, however, the cereal company is giving away 15,000 of the boxes, which will contain nothing but rainbow and unicorn marshmallow bits.

But you can’t just buy it – you have to win it. In order to win a box, you’ll need to enter a code found on the inside panel of specially marked boxes of regular Lucky Charms at MashmallowsOnly.com for a chance to win.

The site also offers mail-in, no-purchase necessary option.