This thing is amazing. I want it to be earlier. I used to use universal caps and they always leaked. He stayed at 15-19 psi. No problems with leaks like everyone else. The easiest and cleanest brake flush I've ever done. The only problem was that the first one I ordered had a broken body (where the nipple was screwed in). Didn't try to check if it's airtight - it looks like an accident because the replacement was fine. Totally worth the $50 - the 43mm fit my is300 and rx350.