Roll up, roll up! You could be the proud owner of an original Banksy sculpture this Christmas. That is, if you can guess how much it weighs. The high-profile street artist announced via Instagram that he is offering the work featuring an overloaded model boat in a raffle to raise money for a charity helping refugees.

The sculpture of the remote-control boat filled with refugees, which featured in Banksy’s “bemusement” theme park Dismaland, is up for grabs if you make a minimum donation of £2 ($2.50) to the charity Help Refugees. With Banksy’s signature dark humor, the competition’s name riffs on the title of the sculpture: How heavy it weighs.

Anyone can make an unlimited number of guesses to the nearest metric unit (grams or milligrams), with the lucky winner to be informed after the competition closes at 8 p.m. on December 22. It’s a tempting prospect given that Banksy’s half-shredded work Love is in the Bin (formerly Girl with Balloon) recently made $1.4 million at auction.

The work under offer is on display at a pop-up “refugee service store,” called Choose Love, in London’s Carnaby Street. Shoppers can also buy practical items, including tents, diapers, and sleeping bags for refugees. You can submit guesses online, and the charity’s website helpfully specifies the dimensions and materials of the object it describes as perhaps both “a darkly satirical work of art” and “a remote-control toy in very bad taste.”

The refugee crisis is a subject close to the artist’s heart. Several works in Dismaland aimed to raise awareness and combat compassion fatigue. The installation at the seaside town of Weston-super-Mare in the West of England ran for five weeks in the summer of 2015. After it was dismantled, the artist donated the wood and other structural elements to help build shelters at the refugee camp in Calais known as the “Jungle.” He also visited the camp to spray-paint a few murals, one depicting the late Apple CEO Steve Jobs, who was the son of a Syrian migrant, and another based on Théodore Géricault’s Raft of the Medusa, depicting refugees on a sinking raft waving for help as a luxury cruise liner breezes past in the distance. Elsewhere, he has painted murals in London and Paris satirizing international institutional responses to the crisis.

How heavy it weighs is on display at Choose Love, 30 Fouberts Place, Carnaby Street, London, W1F7PS.