I initially rated this a one star because like others, was not seeing how this head would ever fit on an Echo SRM-2225 due to lack of instructions and the nut being too big which left me perplexed. However, I reached out to a different seller after trying to get it working by buying another one with different threadings and the same result occurred where the head didn't fit. They sent me a youtube video showing the install process. Once I saw where the error was the install was easy. The error where I was seeing it fail was the post in the first picture that I did not know came off. Once I stuck a screwdriver in the little hole shown in the second picture I was able to remove the post and proceed with the install. Easy to install once you know how it's supposed to go on and the new line is fed easily every time you bump it. The only ding I'll give this is due to lack of original packaging and no instructions shipped with the unit.

Easy to replace the previous head, I have no idea about the durability of the new heads (three). As I mentioned easy to replace it on echo SRM 225. Hopefully it will last longer. Who knows?!