<link rel="apple-touch-icon" href="older-iPhone.png"> // 120px
<link rel="apple-touch-icon" sizes="180x180" href="iPhone-6-Plus.png">
<link rel="apple-touch-icon" sizes="152x152" href="iPad-Retina.png">
<link rel="apple-touch-icon" sizes="167x167" href="iPad-Pro.png">