SelectionGrid texture stretching

Hello!

I have a custom made texture for the buttons which is 12x12 pixels, and it's just a basic color with a 1px black border. Now if I apply this texture to the button via skins, the button looks like I want - all buttons have 1px border (somehow..). If I apply this skin style to the SelectionGrid, it will look bad, because now the texture is like stretched. I've made a picture to represent that:

So, I have 3 questions:

1.Why SelectionGrid looks that bad when I expect it to look the same way as via gui.buttons (since selectiongrid is a set of buttons)?

2.Can I make selectiongrid look the same as buttons with the same texture?

3.How does unity know for buttons how to make a button looks good with this kind of small-sized textures?

Thanks!