WeWork has inked a deal to lease an entire building on East 21st Street for its latest product aimed at midsize firms.

The lease at 35 East 21st St., which was previously Tumblr’s headquarters, spans around 100K SF across 10 floors, the coworking giant announced Friday.

The Centaur Properties-owned building will be dedicated to "HQ by WeWork," the company said in a release. That particular product, launched last month, is aimed at companies with between 11 and 250 employees that want a WeWork-designed, managed and leased offering, but don't want to share it.

The offices would be private, flexible and offer fewer services than a traditional WeWork, but have the benefit of being exclusive to one company. WeWork plans to have 1M SF across the country dedicated to HQ by WeWork by next summer.

“Since we launched HQ by WeWork in July, hundreds of companies have come to us looking for private, flexible and cost-efficient spaces. We are committed to providing them with a working space that allows them to reflect their identity, while enjoying the benefits of being a part of the WeWork community,” WeWork Chief Development Officer Granit Gjonbalaj said, adding that the Flatiron building has a “rich tradition of hosting innovative companies.”

WeWork is now the biggest office tenant in the city, with 5M SF under its control. The company, valued at $20B, became the biggest office tenant in London and Washington, D.C., this year. In New York it has 50,000 members.