This part is no longer available from Yamaha. It has been discontinued. This part is a new reproduction of the original. The originals have deteriorated with time, as they are 50+ years old. The part number is used for reference purposes only and no source of manufacture or supply is implied. These are a great replacement at a fair price. The chrome is comparable to the original. 
 
This listing is for a single fork nut.
 
Part # = 193-23150-40-00
Part Description = OUTER NUT COMPLETE
Model Count = 23
AT1B 1970 125 AT1 Enduro Dual-Purpose 
AT1C 1971 125 AT1 Enduro Dual-Purpose 
AT1E 1969 125 AT1 Enduro Dual-Purpose 
AT1M 1969 125 AT1M Enduro Dual-Purpose 
AT1MB 1970 125 AT1M Enduro Dual-Purpose 
AT1MX 1971 125 AT1MX Enduro Dual-Purpose 
CS3B 1971 200 CS3 Street 
CS3C 1970 250 CS3 Street 
CS5 1972 200 CS5 Street 
CT1 1969 175 CT1 Dual Purpose 
CT1B 1970 175 CT1 Dual Purpose 
CT1C 1971 175 CT1 Dual Purpose 
DT100A 1974 100 DT100 Dual Purpose 
DT100B 1975 100 DT100 Dual Purpose 
DT100C 1976 100 DT100 Dual Purpose 
LT2 1972 100 LT2 Dual-Purpose 
LT2M 1972 100 LT2M Off-Road 
LT3 1973 100 LT3 Dual-Purpose 
LTMX 1973 100 LTMX Off-Road 
MX100A 1974 100 MX100 Off-Road 
MX100B 1975 100 MX100 Off-Road 
RD200A 1974 200 RD200 Street 
RD200B 1975 200 RD200 Street