It seems to be around coarse 60 grit, based on info pulled of an international standard chart with theoretical basic size comparisons. If you inquire back with your contact as to what their metric particle size 0.25mm is compared to in International Standard grit size, this will help you to compare products better.
I personally would be going local, way to many local shops here that conduct this type of work. If I wanted to get the best MF prices for quantity I would be doing an analysis on quantity vs shipping costs, etc. Besides Industry wise I know of some places can produce at a loss and their government will requital their loses to keep their business going, this is another thing killing US manufacturing.
Notice I did say quantity not quality above, which is sad that is the way today's standards are based without knocking anyones' quality.
Was listening to Johnny Cash "Busted" when I was writing this.
http://www.youtube.com/watch?v=4rnAYYh8gGQ
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