Actually the 1/2" is a litlle small. 5/8 or 3/4" is better as it leaves a slightly bigger gap in between the stones. As TD said in his post he uses 5/8" (minus) the minus meaning it has a fairly high percentage of fines (sand and silt). The fines are very important as they fill the voids between the stones allowing it all to lock together when compacted. Most crusher operations produce a lot of 5/8 minus as it is the main specced material used in asphalt production. So you may be able to get a good price on it. other good product per price materials to inquire about are Asphalt reject material. This is material produced that didn't quite meet state or county specs, or came from a pile that had seperation do to to setting and sluffing to long. There is also a material called RAP (recycled asphalt product), where old asphalt is broken up and re-run through the crusher again. This is a nice product because it already has a black color to it from the old asphalt oil. All of the above materials are very nice for driveway construction/maintenance as they compact well and are more erosion reistant.