Per meter
17M (P3) 1960-1964 You need 5m
12M (P4) 1962-1966 You need 4m
17M/20M (P5) 1964-1967 You need 4m
12M/15M (P6) 1966-1970 You need 4m
17M/20M/26M (P7) 1967-1972 You need 4m
OSI 1967-1968 You need 5m
Transit Mk1 1965-1978 You need 4m
Transit Mk2 1978-1985 You need 4m