If more than one part of a silencer attaches to the barrel, each part must be marked.  However, if there are multiple segmented parts, only the parts that can be attached directly to the barrel must be marked. 478.12(b) states in the case of a firearm muffler or firearm silencer, the part of the firearm, such as an outer tube or modular piece, that provides housing or a structure for the primary internal component designed to reduce the sound of a projectile (i.e., baffles, baffling material, expansion chamber, or equivalent). In the case of a modular firearm muffler or firearm silencer device with more than one such part, the terms shall mean the principal housing attached to the weapon that expels a projectile, even if an adapter or other attachments are required to connect the part to the weapon. The terms shall not include a removable end cap of an outer tube or modular piece.