Woosung is the core casing manufacturer of welch crv pumps. The original importer was cacegen untill the manufacturer boned her and sold the line to welch. Other than the casing and some seals and everything inside they are core made in korea I think and shipped all over from xd to welch to cacejen. Woosung is a huge rip off vacuum pump company that coppies literally everyone from Edwards to leybold. Welch just slaps a label on it. You can call woosung and get those pumps delivered to your door with your name printed on it.
Also don’t put words in my mouth. All pumps will eventually work on something. But you aren’t always reaching the cusp of the vacuum range during opperation then you won’t be sinking your opperation temps and increasing efficiency. I know people who use pumps smaller than a Edwards 30 on a single pump 22l. I personally always encounter thier extended happiness when they eventually drive the vacuum cusp lower achieving a better spd performance. My 2 cents.
Also I size pumps differently. I’m not scared to add hardware to a spd to make it behave like a bat out of hell.