If you mean the cover that Hi - Lift sells, I got one for my 60" jack and it doesn't cover the (critical) bottom end, where protection would be good. I have no idea why they just wouldn't extend the damn thing another few inches so it would be worth having. It's on my list to just make a cover that will actually cover it.
Now it's mostly just a PITA.
It would work OK on the 48" jack I suppose, but depending on how you mount the jack you might have to poke a hole in the cover somewhere. I had to do that too.