http://www.bbimporters.com.au/search/index.php?step=5&make=SUZUKI&model=RM125&year=1980&category=Connecting+rod+kitThis is Pro X brand kit
Current part numbers
Rod
Part # = 12161-39300
Part Description = ROD,CONNECTING
Model Count = 48
A100M 1976 98 A100 STREET
DS100C 1978 100 DS100 DUAL PURPOSE
DS100N 1979 100 DS100 DUAL PURPOSE
DS100T 1980 100 DS100 DUAL PURPOSE
DS100X 1981 100 DS100 DUAL PURPOSE
DS125C 1978 125 DS125 DUAL PURPOSE
DS125N 1979 125 DS125 DUAL PURPOSE
DS125T 1980 125 DS125 DUAL PURPOSE
DS125X 1981 125 DS125 DUAL PURPOSE
RM100A 1976 98 RM100 OFF ROAD
RM100N 1979 98 RM100 OFF ROAD
RM100T 1980 98 RM100 OFF ROAD
RM100X 1981 98 RM100 OFF ROAD
RM125B 1977 123 RM125 OFF ROAD
RM125C 1978 123 RM125 OFF ROAD
RM125-M 1975 123 RM125 OFF ROAD
RM125-N 1979 123 RM125 OFF ROAD
RM125-T 1980 124 RM125 OFF ROAD
RM125-X 1981 124 RM125 OFF ROAD
RV125A 1976 123 RV125 TRACKER DUAL SPORT
RV125B 1977 123 RV125 TRACKER DUAL SPORT
RV125K 1973 123 RV125 TRACKER DUAL SPORT
RV125L 1974 123 RV125 TRACKER DUAL SPORT
RV125M 1975 123 RV125 TRACKER DUAL SPORT
TC125A 1976 123 TC125 PROSPECTOR DUAL SPORT
TC125B 1977 123 TC125 PROSPECTOR DUAL SPORT
TC125J 1972 123 TC125 PROSPECTOR DUAL SPORT
TC125K 1973 123 TC125 PROSPECTOR DUAL SPORT
TC125L 1974 123 TC125 PROSPECTOR DUAL SPORT
TC125M 1975 123 TC125 PROSPECTOR DUAL SPORT
TM100L 1974 98 TM100 CONTENDER OFF ROAD
TM100M 1975 98 TM100 CONTENDER OFF ROAD
TM125L 1974 123 TM125 CHALLENGER OFF ROAD
TS100C 1978 97 TS100 HONCO DUAL SPORT
TS100N 1979 97 TS100 HONCO DUAL SPORT
TS100T 1980 97 TS100 HONCO DUAL SPORT
TS100X 1981 97 TS100 HONCO DUAL SPORT
TS125A 1976 123 TS125 DUSTER DUAL SPORT
TS125B 1977 123 TS125 DUSTER DUAL SPORT
TS125C 1978 123 TS125 DUSTER DUAL SPORT
TS125ERT 1980 124 TS125R DUAL SPORT
TS125J 1972 123 TS125 DUSTER DUAL SPORT
TS125K 1973 123 TS125 DUSTER DUAL SPORT
TS125L 1974 123 TS125 DUSTER DUAL SPORT
TS125M 1975 123 TS125 DUSTER DUAL SPORT
TS125N 1979 125 TS125 DUSTER DUAL SPORT
TS125R 1971 123 TS125 DUSTER DUAL SPORT
TS125X 1984 124 TS125X DUAL SPORT
Big end pin
Part # = 12211-03020
Part Description = PIN,CRANK
Model Count = 17
DT16B 1976 284 DT16 OUTBOARD
DT16C 1977 284 DT16 OUTBOARD
DT16D 1978 284 DT16 OUTBOARD
DT16F 1979 284 DT16 OUTBOARD
DT16G 1980 284 DT16 OUTBOARD
DT16J 1981 284 DT16 OUTBOARD
DT99C 1977 152 DT9.9 OUTBOARD
DT99D 1978 152 DT9.9 OUTBOARD
DT99F 1979 152 DT9.9 OUTBOARD
DT99G 1980 256 DT9.9 OUTBOARD
DT99J 1981 256 DT9.9 OUTBOARD
RM100N 1979 98 RM100 OFF ROAD
RM100T 1980 98 RM100 OFF ROAD
RM100X 1981 98 RM100 OFF ROAD
RM125-N 1979 123 RM125 OFF ROAD
RM125-T 1980 124 RM125 OFF ROAD
RM125Z 1982 124 RM125 OFF ROAD
I would say that its just the length that is the difference. TS, TC, TM, DS etc probably use a different length rod
Ebay should be the cheapest