The 240-mm self-propelled mortar known to the West as the M-1975 is known as the SM-240 (2S4) by the former Soviet Army, although its more common name is the Tyulpan, or Tulip Tree. The M-1975 consists of a much modified GMZ tracked minelaying vehicle carrying a 240-mm M-240 breech-loading mortar on the hull rear. The mortar is carried complete with a baseplate and is hydraulically lowered from its traveling position around a pivot on the hull rear. The baseplate is hinged to the hull rear so that when emplaced the mortar barrel faces away from the hull. The 240-mm mortar is lowered into the firing position under remote-control and when in position can be elevated from +45 to +80° with a traverse of 8° left and right. Some rounds are probably carried inside the vehicle hull and it is likely that some form of assisted loading is provided. The rate of fire is probably about one round a minute, with firing being by remote-control. The hull of the vehicle is of all-welded steel armor with the engine compartment at the front right and driver front left. The commander is seated to the rear of the driver and has a raised cupola with an externally mounted 12.7-mm anti-aircraft machine gun. A further hatch is to the rear of the commander's cupola with a similar outward opening hatch on the opposite side of the vehicle roof. Ammunition is stowed internally and is loaded into the mortar using a hand-operated crane mounted at the rear of the vehicle on the left side.

The mortar sighting system is on the right side of the mortar. Suspension is of the torsion bar type with each side having six road wheels with the drive sprocket at the front, idler at the rear and four track-return rollers. Firing a standard 130 kg HE round designated the F-864, a minimum range of 800-m and a maximum range of 9700-m can be achieved. In addition there is understood to be an extended-range round with a maximum range of 20000 m. Other rounds include a chemical projectile and nuclear. A concrete-piercing round for use against urban targets has been reported.