We offer this Conical Inner Neck Seal design with an 8-inch mounting diameter that is found on Viking brand and many other brand drysuits. If you are going to glue the seal to the inner part of the suit the inner seal design may work better, although some people still prefer inner mounting a standard bellows design neck seal. Conical inner neck seals are available only in 0.7-1.0mm standard thickness and two sizes; the medium is 10-inch in circumference and fits 11-inch to 13-inch necks, the large is 12-inch circumference and fits 13-inch to 16-inch necks.