The first M-25s were produced from kits imported from the United States; the main difference between the later M-25 and the R-1820-F3 was the use of metric components. 13,888 M-25s were produced in the USSR at factories in Perm and Kazan. There were a number of sub-variants which differed from the original M-25 in that they had reduction gears, rather than direct drive.