.bapf_ckbox_square input[type=checkbox] {
    -webkit-appearance: none;
    -moz-appearance: none;
    -ms-appearance: none;
    appearance: none;
    display: inline-block;
    vertical-align: middle;
    border: 2px solid #555;
    width: 20px;
    height: 20px;
    outline: none;
    padding: 4px;
    margin-right: 5px;
}

.bapf_ckbox_square input[type="checkbox"]:checked {
    background: #555;
    background-clip: content-box;
}