.m-thumb {
   display: inline-block;
   vertical-align: middle;
   margin-right: .3em;
}

.m-thumb img {
   -webkit-filter: grayscale(1);
   -moz-filter: grayscale(1);
   filter: gray;
   width: 70px;
   opacity: 0.5;
}

.m-thumb:before {
   display:none;
}

.m-thumb:hover img {
   -webkit-filter: none;
   -moz-filter: none;
   filter: none;
   opacity: 1;
}