Moonalice, whose song “It’s 4:20 Somewhere” has been downloaded over 2.5 million times, will celebrate 4/20 with a special benefit show. The group—whose lineup includes Roger McNamee, John Molo, Barry Sless and Pete Sears—will perform at San Francisco’s Slims tomorrow night.

Wavy Gravy will host the tribal pow-wow, and an onsite silent auction will benefit Sweet Relief, specifically their friend Jim King. Some items up for auction include a White Fender Stratocaster signed by Carlos Santana and a Zildjian cymbal autographed by all members of Metallica, among many others.

In addition, Moonalice, famously supporters of poster art, have created a record 15 posters for the holiday by famous artists including Stanley Mouse, Dennis Larkin and Lee Conklin. A special Moonalice 4/20 “widget” also has been created and will have a gallery of the days poster art, a link to download “it’s 4:20 Somewhere,” a link to the song’s video as well as band info and the ability to share via email and social media.