The mufflers show up, do the swap. No down time. They send a return label with your order. Just stick old mufflers in the same box and stick the label on. The refund of the core charge also happens as soon as they receive the cores.
overall a great buying experience and love the sound. You may save a couple bucks finding a muffler shop to hack up your mufflers, but they will likely never have done it before. These come with perfect welds and painted like new