SM53, originally designed MBO and colloquially known as Høka, were a class of 58 trams and 50 trailers built by Høka and Hägglund for Oslo Sporveier. The units were used on the Norway's Oslo Tramway from 1952 until 2000. The long and wide trams weighed . They had four motors providing a combined power output of , allowing for a top speed of .
The first series of thirty trams in 1950, with delivery in 1952 and 1953. These were designated MBO50. The next order was for new bodies for used Class SS units. The eight motor units were designated MO and nicknamed Chickens, while the twelve trailers were designated TO. These twin-axle units proved unsuccessful and Oslo Sporveier therefore took deliver of more MBO units. The next batch of twelve MBO55 units were delivered in 1957 and the final batch of eight were designated MBO56 and delivered in 1958. These were built for use on the Lambertseter Line, but were found unsuitable for use on light rail service and later moved back to the street