Myosin filament : Each myosin (thick) filament is  a polymerised monomeric proteins. The monomeric units are called Meromyosins. These constitute make one thick filament.

Each meromyosin has two important parts, a globular head with a short arm and a tail, the former being called the heavy meromyosin (HMM) and the latter, the light meromyosin (LMM). The HMM component, i.e.; the head and short arm projects outwards at regular
distance and angle from each other from the surface of a polymerised myosin filament and is known as cross arm. The globular head is an active ATPase enzyme and has binding sites for ATP and active sites for actin.

Thick filament (above) and a myosin molecule (below)