Will this work on my lowering springs or just stock springs?

Spring compressors are rated for a range of spring rates. Verify your spring's rate (usually marked on the coil) falls within the tool's capacity before clamping — stiffer aftermarket springs sometimes need higher compression force than stock.

Do I need a jack or press to use this?

You'll still need to support the vehicle on jack stands and remove the wheel and strut assembly. The compressor itself handles the spring tension once the assembly is on the bench — no hydraulic press required.

What do I do if the compressor won't fully close on my spring?

Loosen the adjustment points and reposition the clamps closer to the coil's center. If the spring diameter is significantly outside typical range, test-fit the tool before fully committing to a job — oversized or undersized springs may not seat properly.