There are 43 configurations available for the Series II connectors, ranging from shell-size 9 to shell-size 25. High density is achieved by use of size 22D contacts (up to 128 contacts in a size 25 shell). The standard product features crimp contacts but other options for termination include soldering and PC tail. Mating discrimination is provided by five unique key patterns, allowing multiple pairs to be placed in proximity without the risk of cross-mating.