Baseplate protein that is located next to the tail tube (inner baseplate) (PubMed:27193680). Involved in the tail assembly (PubMed:21129200). The gp25-(gp6)2-gp7 module is involved in sheath contraction (PubMed:27193680). Homodimer (PubMed:2403438, PubMed:19896486, PubMed:27193680); each gp6 molecule in the ring interacts with its two neighbors, forming an N-terminal dimer with one and a C-terminal dimer with the other (PubMed:27193680). Heterotrimer with gp7; gp6 is part of a (gp6)2-gp7 heterotrimeric molecule (PubMed:27193680). The (gp6)2-gp7 heterotrimeric molecule further interacts with gp25 and gp53; the gp25-(gp6)2-gp7 module is involved in sheath contraction (PubMed:27193680). Part of the baseplate macromolecular complex which consists of gp5, gp5.4, gp27 (central spike complex); gp6, gp25, gp53 (inner baseplate); gp7, gp8 (intermediate baseplate); gp9, gp10, gp11, gp12 (peripheral); gp48 and gp54 (proximal region of the tail tube) (PubMed:27193680). 12 copies of gp6 form a continuous ring that makes up most of the inner baseplate. Expressed in the late phase of the viral replicative cycle. Belongs to the T4likevirus baseplate wedge protein gp6 family.