Seaslug was a high-performance weapon in the 1960s, with a single-shot kill probability of 92%, although other sources give lower kill probabilities: 75% for the Mk 1 and 65% for the Mk 2. The first four ships of the "County"-class (Batch 1) operated the Seaslug Mk 1, while the final four (Batch 2) were fitted with the ADAWS command and control system which enabled them to carry the more capable Mk 2 version. A proposal to refit the Batch 1 ships with ADAWS was dropped in 1968.