Builders must support the builder specs, either by using builder geth or developing customized software, and then contact bloXroute support for builder registration. Builders must have Ultra tier in order to connect to bloXroute relay in Mainnet, or Introductory tier in Ropsten. Builders can start submitting full blocks to bloXroute now!
Some builders will be able to get from bloXroute MEV bundles and private transactions to be added to their blocks. Builders will need to be whitelisted by bloXroute.