I bought these tuners for a telecaster-building project, which is now, happily completed.
They are very nicely made, with nice surface and good quality chrome, and adds a sense of quality to my guitar head.
The locking mechanism works perfectly.
At installation, beware that these tuners do not use a screw to avoid rotation as many other tuners do. Instead they have two little metal tabs that have to fit into the guitar head, and which you have to make (drill) little holes for, However, once installed they are very elegant, and will never be able to rotate,
When the strings have been installed "finger tight" you only have to rotate them about a quarter of a turn (about 4-5 full turns of the tuner head, which has a nice 1:16 gearing) and you will be in tune, and STAY in tune (except for string-stretching, which is less than on traditional tuners, since the twirls around the tuner-head are avoided).
The tuners axis is shortened, compared to a traditional tuner (since you dont need the string to swirl around it several times) so the angle from the nut, even to the high E tuner (on a telecaster head) is enough to avoid using a string-tree, and hence avoid friction from this.