Although it is rare to get out first, I purchase a lock attachment so that couplers who did not fall as a customer 's vehicle will not fly. I also tried the resin, but again the robust metal is suitable for our use. Again, there is only Nitto san! I can not complain. And although it is an exchange this time, the thing which I used until now is using for about 10 years, but there is not air leak at all.