Responsive Social links profile page

The only thing I found challenging was picking between using buttons or <a> tags for the links. I could easily change the width and height for the buttons but then again the background colour seems off. While creating borders for the <a> had to be separately for each. Eventually I went with the <a> tags. Uhm, I don't think I have any code that am unsure of. Yes, My question is there a simpler way of making sure the border for <a> tags have the same width despite having a difference in character amount?