product conforming in appearance but lacks the function of trimming the diopter ring

I put 3 stars because in the presentation of the product on Amazon (with translation in English with a ladle!) I understand that the diopter ring (diopter corrector is a device for adjusting the viewfinder depending on the view of the user.) If this ring exists it has no function. I had seen that same reflection on a product of this brand version below that I have taken, I thought that taking the VF SK-130x more expensive I would not have this problem.
If the eyepiece is flexible and very wide, comfortable for eyeglass wearers. The plate that attaches can remain in place and serves as a base (the device posed remains stable) by against his mounting screw is really a screw so you need a screwdriver or a coin to tighten while on some models This is a screw with a half ring which allows hand tighten, even more convenient when you're on the field