I want your help please to choose the correct saddle.My bones measuring is 112mm , and i am between Romin Evo Expert Gel and Specialized Power Expert Saddle can you answer me witch is the right saddle for me 143 or 155 ?
I cannot tell you which one because everyone is different. You need to test each saddle You can almost always try out a saddle and return it if it doesn't work for you. Bike shop people know it takes some time and testing a couple saddles to find the right one.
Consider is your riding style and what kind, like road or mountain biking, and if you're doing long distance touring, say, versus competitive time trials or triathlons.
Finally, keep in mind that women have wider "sit bones" than men and bike companies carry women's saddles. Most bikes come with a men's saddle. A woman riding a men's saddle can have a lot of discomfort! When I worked in bike shops, a lot of ladies didn't realize they'd needed a better saddle.
I think you are looking for a chart like the one below that translates your sit bone width (which I assume is 112 mm - you only specified your "bone" measurement) into a Body Geometry (BG) saddle width (pictured below). Your final width depends on a combination of your body position (and riding style) in addition to your sit bone width. Likely you will need a 143 mm saddle. Finally, this final saddle width is independent of saddle style (i.e., Romin vs. Power). I believe the Power is intended for more aerodynamic positioning and lets you position the saddle farther forward towards the bottom bracket, but still remain UCI legal (i.e., not less than 5 cm from nose to BB). The downside is the Power really only has one riding position, while something like a Romin should have more positions which can be better for longer rides.