The ships were wooden-hulled, with steam power as well as sails, but of shallow draft for coastal bombardment in the shallow waters of the Baltic and Black Sea during the Crimean War.

[1] Ten ships had two-cylinder horizontal single-expansion trunk steam engines built by John Penn and Sons, with two boilers.

The other ten had two-cylinder horizontal single-expansion direct-acting steam engines built by Maudslay, Sons and Field, with three boilers.

Both versions provided 60 nominal horsepower through a single screw, sufficient for 7.5 knots (13.9 km/h; 8.6 mph).

[1] Ships of the class were armed with one 68-pounder smooth bore muzzle loading cannon (SBML), one 32-pounder SBML (originally two 68-pounder SBMLs were planned but the forward gun was substituted by a 32-pounder) and two 24-pounder howitzers.