The MPR-M85 limpett mine was designed primarily for land-based sabotage missions although it can be used underwater at depths of up to 10 m.
It is a circular mine with an electronic time fuze, and contains 400 g of plastic penthrite /PEP/, a PETN-based explosive.
Before placing the mine in position, the electronic timing delay is set manually. Delays are 15 or 30 minutes, then 1, 2, 4, 8 and16 hours.
Once the delay has been set, a safety pin is removed and there is an arming time of 7.5 minutes before the fuze is armed.
On detonation, the mine can penetrate up to 15 mm of steel plate.
After the mine has been armed, an anti-disturbance fuze has been set to prevent removing.