1. Larger pitch distance for type A thread,sharp point , outer diameter is more larger than thread type B , is available for below 1.2mm thikness of panels
2. Flat point for thread type B , just like thread AB type , beside same thread Number  per inch , this kind of thread is good choice for thinkness from 1.2mm to 5mm .
3. Type AB thread which is same as type B , but Type AB is more faster than Type B in drilling speed .