Hercules Key Features and Benefits:

Easy interface and workflow, making the musculature setup quick, effective and easy to to integrate within your current production pipeline.
 
Fast secondary motion dynamics (spring-based) on muscles.
 
Back transformation, to avoid double transformations when muscles are linked to another master node, very handy in most character setups.
 
No object restrictions, any type of objects, not only Muscles, can be used as deformer objects!

Fully compatible with most character animations plug-ins, including Skin, Physique, Bones Pro and Biped.
 
 And so much more!