The bigger the lobster, the stronger the claws. My claws are large--bigger than your hands and are extremely powerful  in the grasping direction. The bigger of the two claws is the crusher claw and mine can crush your fingers flat. It is designed to crush the shells of clams, crabs, mussels and other prey. I am left handed. Lobsters that have their heavy ("crusher") claw on the left side are considered "left-handed". During lobster to lobster combat, two lobsters sometimes will grab each others crusher claw and have a showdown of muscle and shell strength.The smaller claw is the pincher claw, also called the cutter or ripper. The pincher claw has a fast-acting muscle tissue useful for grabbing prey quickly.  Most people fear the crusher claw, but you'll get a nastier wound from the pincer claw if it latches onto soft tissue. Thick rubber bands are also used to restrain these claws. But in my case lobstermen will often use electrical tape since the normal bands are not big enough.