.product-thumb .button-group button 
{width: 80%;
}
@media (max-width: 1200px){
.product-thumb .button-group button, .product-thumb .button-group button + button 
{width: 50%;
        }
}
@media (max-width: 767px){
.product-thumb .button-group button, .product-thumb .button-group button + button {
width: 50%;
        }
}