hi,my name is mike, ido not speak english very well.... hope not to write to bad... ;D. i am using winstep extreme and making also some skins. my serious problem is that the bars and shelves have a strached part. i need a perfect size ( in pixels or cm ) for every bar and shelves,
<The reason for this,is that i need to make some shaddow effects in the middle of bars....
the main shelve has the strached part in the middle ... i tried to make my own dimensions...but is not working like i would like......
hope u can help me

No, you don't need any "perfect" size. You just need to adjust the width of the parts that get resized and the parts that don't get resized (slices).
You're obviously copying some other theme and its slices don't work for you, that's why you think you need a size. Open the theme settings files and tweak the slices yourself. Any image size will do, then.