Differences

The biggest difference between a mini perforation and a standard perforation is the number of teeth on cutting wheel used to make the perforation on the paper or plastic. A standard perforation wheel normally has between 2 to 16 cuts per inch.  While a mini perforation has between 30 and 72 cuts per inch. Below is a picture showing how the two look when compared to each other on a piece of paper.

 

 You can easily see that the standard perforation has longer cuts and larger gaps between each cut.  The mini perf has many more individual cuts and much smaller spaces between each cut. Normally the standard perforation wheel would use between a .020" and .040" tie ( gap between cuts ), while a mini perf would use between .004" and .008" ties.  The ties or uncut portion of the material is what holds the material together.  You can also see by looking at the pictures above that when the paper is torn off along the perforations the standard perf will have much larger pieces of material sticking out compared to the mini perf.  In fact the mini perf will almost look like a cut edge. When you compare the amount of material that is uncut to the amount of material that is cut, that is called the % of hold.  This is a rough measure of the strength of the perforation.

Different Types

The normal range of products varies from 30 cuts per inch up to 72 cuts per inch.  Mini perfs are available in two broad groups based on the depth of the teeth in wheel. The first group uses a tooth depth of .010" and the second group uses a tooth depth of .030".  Below are two charts showing the basic product ranges
  
 

Why use the different tooth depth?  The smaller tooth depth is used single sheets and thinner materials, while the second depth (.030") is used for thicker materials and can be resharpened if done very carefully.