Letton
The boats were small coastal submarines built to a French design. Ronis means "seal" in the Latvian language, Spīdola is a character from the Latvian language poem "Lāčplēsis". The submarines were long overall with a beam of and a draught of . The vessels of the class displaced surfaced and submerged. The submarines had a dived depth of . They had a complement of 27 officers and ratings.