I have the Samsung Galaxy 4 Classic 46mm with a black plastic strap. Trying to replace it, I noticed that the width of the leather at the hook point was larger than the gap in the watch. I cut a small piece of the leather thinking that this was preventing the clasp from closing. Still, the clasp wouldn't close.
I removed one of the clasps from the original plastic strap and measuring it with the caliper, it was over two millimeters smaller than the new one, which of course never fit since it didn't fit into the gap at the end of the watch.
I have kept the unused strap as a souvenir of false promises.

From and Closed it is supposed to be made of leather this thing. If it is then it has undergone excessive processing to look quality and this betrays it. Not at all. For the same money, a simple smooth leather strap without stitching is what is needed for the watch. In black, the poor quality is not as noticeable as in brown!

First of all, if it is leather (it looks more synthetic), it is of very low quality or excessively processed. The color resembles orange rather than the light brown in the photo. I would recommend a better leather strap in 20mm from the countless options available on Scroutz or in a store. The same applies to the black one.