MK3-P2 indicates pin 2 of the XLR is tied to the tip of the 1/4" plug (pin2 hot). 
MK3-P3 indicates pin 3 of the XLR is tied to the tip of the 1/4" plug (pin3 hot). 
The remaining pins of the XLR are tied to the shield of the 1/4" plug. 

Stock lengths are 3', 10', 18.5' and 25' for both MK3 models.