We look for items from the time to time that work well with our manufacturers' abilities as well as the need of the general collecting public and this time, we really did a great job. It seems that there are just tons of lunch boxes out there that are missing the spring that holds the thermos in place for some reason. I am not sure why, maybe someones grandfather needed it to fish a wedding band out of drain. Not sure, but for some reason, they are all missing. This one fits many different styles of lunch boxes from the 50s to the 70s. If you are not sure, google the lunch box that you have and see if someone else has a picture of it, with its original spring, just to make sure before you buy it! PS. Professional lunch box sellers are out there buying them in 10s and 20s so the next time you go to the flea market and that spring looks too good to be vintage, it is probably one of ours!