Elon Musk revealed new details on Thursday about The Boring Company’s upcoming bricks. The tunnel-digging venture plans to use leftover dirt from its projects and package them into the product, cutting back on carbon emissions from concrete production. The company plans to start selling the bricks in two months’ time at a price of 10 cents per brick — giving them away for free when used for affordable housing projects.

The details are the latest in Musk’s plan to revolutionize the tunnel-digging industry, after announcing the plans in May 2017 and providing more details the following March. The company claims that concrete production covers around 4.5 percent of greenhouse gas emissions, meaning bricks built from leftover tunnel dirt would help reduce some of this production. The prices compare reasonably to other market options. RemodelingCalculator.com estimates brick prices ranging anywhere from 34 to 85 cents each, but a myriad of factors like style, supplier, and quantity make direct comparisons difficult.

See more: Elon Musk Just Revealed The Boring Company’s Eco-Friendly Plan for Old Rock

Reusing tunnel rock is not a novel idea. Crossrail, the London project to build a 13-mile tunnel under the city as part of a 73-mile railway, has diverted around 98 percent of 389,068 tonnes of material away from landfill. Similarly, debris from New York’s Second Avenue subway was used to create a golf course in the Bronx, with the rest either sent to a recycling plant or a New Jersey landfill. However, Musk’s decision to use the rock in a consumer-facing product could encourage consumers to build using more sustainable materials.

Musk previously announced the interlocking bricks will have a “precise surface finish,” so two people can build outer walls for a new house in just one day. They’re rated for California seismic loads, but they’re bored in the middle like an aircraft wing spar to cut down on weight. The first set, anticipated to be themed around ancient Egypt, is expected to ship worldwide.

The bricks have already seen at least one public outing, used to craft a podium for Musk at the SpaceX hyperloop speed competition on July 22. Buyers will be able to construct their own podiums, alongside other projects, when the store opens in the next two months.

Read More on The Boring Company

Photos via Flickr