Perhaps a bit expensive, but it does the job. All 4 brake pistons all move at the same time now.

Perfect for servicing Hope calipers. Could only be improved by having a nail polish style brush on the lid. I ended up using cotton buds which weren't great for the job.

Sorted sticking piston issue with Tech 4 brakes

Does the job well. You only need the smallest amount to keep your piston running smooth.