The NATO reporting name for the class is Losos, which means "salmon" in the Russian language.

The Losos class was designed for special operations and engaging surface ships located offshore, and is thus very durable and almost completely silent.

[citation needed] The hull is made of a titanium alloy, which helps with signature management because it is not magnetic.

The non-magnetic alloy would greatly reduce the effectiveness of enemy magnetic anomaly detectors or magnetic limpet mines against this type of vessel.

Original planning called for a total of 12 Project 865 Piranha submarines to be constructed; this was eventually reduced to six, then just the two.