When its said Waterproof Rating : 5000mm...
When its said Waterproof Rating : 5000mm what's is mean ?
I'll spare the technical aspects...
Basically, waterproofing for snowboard gear is typically either 5000mm, 10000mm, 15000mm, or 20000mm (for high-end, expensive stuff). The higher the #, the less water will penetrate the fabric. 5000mm often works well, but if it's rainy or icy out, after awhile you'll start to feel the moisture getting through. 10000mm or 15000mm is (in my opinion) a good # for pants, especially if you're planning on spending some time playing in the snow (as opposed to on it).
In short, 5000mm is decent for a jacket (bare-minimum), but you'll feel moisture after a couple mins of leaving snow on your jacket; it's what I ride, and I'm fine with it (but my pants are 15000mm).
If that doesn't answer your question well enough, dive in here: http://backcountrybeacon.com/2010/04/waterproof-ratings-demystified/