JSFiddle - React, Tailwind, and code Playground

HTML

<button>КНопко</button>

CSS

button {

    box-shadow: inset 0px 1px 0px 0px #f7f7f7;
    background: -webkit-gradient( linear, left top, left bottom, color-stop(0.05, #ededed), color-stop(1, #dfdfdf) );
    background: -moz-linear-gradient( center top, #ededed 5%, #dfdfdf 100% );
    background-color: #eee;
    font-size: 15px;
    font-family: MyriadPro;
    border-radius: 2px;
    border: 1px solid #cecece;
    display: inline-block;
    width:182px;
    height:32px;
    position:relative;
    text-align:left;
    padding-left:10px;
}
button:before {
    position:absolute;
    display:block;
    content: "";
    top:0;
    right:0;
    width:29px;
    height:30px;
    border-left:1px solid #fff;
    background:transparent;
}
button:after {
    position:absolute;
    display:block;
    content: "▼";
    line-height:32px;
    font-size:12px;
    text-align:center;
    top:0;
    right:0;
    width:30px;
    height:30px;
    border-left:1px solid #cecece;
    background:transparent;
}

button:hover {
    background: -webkit-gradient( linear, left top, left bottom, color-stop(0.05, #dfdfdf), color-stop(1, #ededed) );
    background: -moz-linear-gradient( center top, #dfdfdf 5%, #ededed 100% );
    background-color: #dfdfdf;
}

button:active {
    position: relative;
    top: 1px;
}