Something to keep in mind. At your local feed store they most likely don't get many requests for rodent lab block compared to the other items they sell, so most times the people working there will not be familiar with the Mazuri 6F.
Also many of these places don't carry 6F in stock but can order it and have it come in with their normal supply truck shipment.
In either case you need to approach them armed with knowledge. Remember the product code for Mazuri 6F is "5M30".
Also, the store I've bought the 6F from before didn't know what I was talking about until I told them Mazuri was a Purina brand, then they were able to figure out they could special order it with their normal Purina shipment.
And if all else fails as I said before you can order Harlan/Native Earth 4018 online from National Pet Pharmacy, which is only $.53 a pound for one 40 pound bag or $.38 a pound for five 40 pound bags shipped to your door (tax free in most cases), compared to paying a typical $30 for a 50 pound bag or Mazuri 6F at your local feed store( .$60 a pound + sales tax and round trip gas).
I honestly just can't believe what a great deal National Pet Pharmacy has.