I'm still impressed beyond words that they were able to glue basically 2 reused rockets onto a 3rd rocket and then not only have a successful test flight but return 2 of the 3 boosters.
Fun fact: there is a pneumatic mechanism that gives the side boosters a gently push away at the top, with the bottom attachment point separating milliseconds later. This is to cause the side boosters to fall away from the center core properly.