They were constructed entirely of steel, and had three decks, the lower one having loophole shutters for infantry fire.

On the upper deck, which was extended over the whole length of the boat, was a conning tower.

In the after portion of the boat, and beneath the upper deck, were cabins for officers.

Each boat carried a twelve-pounder quick-firing gun forward, a howitzer, and four Maxims.

The craft were a hundred and thirty-five feet long, with a beam of twenty-four feet, and drew only three feet and a half of water.