The self-lacing sneakers that Michael J. Fox wore in Back to the Future II are now a reality, and Nike has set up a way to win a pair through the crowdfunding platform RallyUp as part of a promotion for the Michael J. Fox Foundation.

The self-lacing shoes first appeared in the sci-fi film in 1989. But Nike has been working on the real technology since 2011, and the company has been showing off the shoes since last year. Today, Nike said it will have a limited-edition release of its second-generation Nike Mag shoes.

Using RallyUp’s platform, Nike is opening an online raffle for consumers to win a pair. Tickets sell for $10 each, and entrants can buy as many tickets as they want. Every donation will go to the Michael J. Fox Foundation, which is trying to find a cure for Parkinson’s disease.

Nike said it will take its “power-lacing” technology to more products.

According to Nike, there are only 89 pairs available, in men’s size 7, 9, 11, and 13. The Draw, as the company calls its online raffles, is open from today until October 11, with the winners set to be contacted on October 17.

RallyUp, founded by technology entrepreneur Steve Bernat, is an all-in-one fundraising platform for charitable organizations.