Here's what happened. I put all new brakes, hoses, wheel cylinders etc. on my '65 Barracuda. I also converted to a dual master cylinder and had the booster rebuilt by Booster Dewey. It's a long story, but I was having a hard time getting a hard pedal after bleeding. I had used my Miti-Vac vacuum pump and then had Mrs. Big John doing the traditional job of working the pedal for a pressure bleed. It still wasn't going right. One thing lead to another and I bought two things... These are master cylinder plugs. Unscrew the lines into the master cylinder one at a time and they can easily tell you if the problem is front or rear. https://smile.amazon.com/gp/product/B07N18QS7Y/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1 I also bought one of these... A Motive Power brake bleeder. https://smile.amazon.com/gp/product/B00CJ5DY16/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1 I've always wanted something like this and now I don't know why I waited. The flat plate clamps over both sides of the master cylinder. (other adapters for new cars available) with some J-hooks and chains. I couldn't get it to not leak, so I added a C clamp and it worked perfectly. Basically, this is a garden sprayer... Fill it with brake fluid and pump it up to 15-20psi and start bleeding. This worked fantastic for me... After bleeding everything again, I narrowed my problem down to the front brakes using the plugs and then figured out it was a bleeder in the Chineasium wheel cylinder. A little extra torque with a socket has it working for now. I'll find some USA built cylinders at Carlisle or eBay and rebuild them. The only downside is you are supposed to use 2 quarts of brake fluid... I had most of a quart and didn't feel like driving to the store. It worked, but it did push a lot of brake fluid through, so next time I'll fill it up. So... Great piece, well built, good price. Should have bought one of these years ago! I found a short video of it in use.