Professional Gray Zebra Nail Files, these are very thick boards, nice a foamy.  The coarse material is on both sides, so you able to use both side for your nails.  These are a really nice size board, easy to grip and hold.  The boards do a great job on my nails, and even my daughter in law whom has acrylic nails, so these works great on both.   Thank you for allowing me to try your product  I recommend this product. Disclosure: I received this product at a discount in exchange for my honest  and unbiased review.  I have no affiliation with this company.

http://www.amazon.com/Professional-Gray-Zebra-Nail-Files/dp/B01A1BR9AG/keywords=nail+files

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