A millable bridge plug system includes a mandrel having an upper portion and a lower portion, a shearing member attached at said upper portion of the mandrel, a sealing member, ring members, cone assemblies, slip devices, and a cap member at a lower portion of the mandrel. The shear member and the cap member are modular so that one bridge plug interchangeably connects to another bridge plug. The shear members are compatible with cap members of other bridge plugs. The shear member and the cap member further include a locking mechanism for rotational engagement by protrusions on the cap member being fit into the shear member and a locking mechanism for triggering a spring loaded lock into a groove on the cap member.