SBXi is a venture fund backed jointly by eight firms—including Accel, General Catalyst, Polaris, Pillar, Glasswing, Underscore, Danaher, and GETTYLAB—and it invests only in startups with at least one MIT graduate on the team, having grown out of MIT Sandbox's post-graduation funding gap. It moves quickly and predictably, promising a response within two business days, a decision within seven, and a guaranteed yes or no for every eligible company, while offering flexible funding from $10K–$100K SAFEs up to $100K–$1M checks that can match outside lead investors' terms.