.productbtn{
  position: relative;
}

.menu{
  position: absolute;
  left: 50%;
  z-index: 999;
  /* top: 40px; */
  transform: translateX(-50%);
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  transition: all 0.5s;
  width: 122px;
  height: 0;
  overflow: hidden;
  background-color: #fff;
  box-shadow: 0 2px 4px 0 rgba(132, 132, 132, 0.5);
}
.productbtn:hover .menu{
  height: 132px;
}
.header .item li.productbtn .menu a{
  background: none;
  font-size: 11px;
  color: #000;
  margin: 0 0 4px;
  width: 100%;
}
.header .item li.productbtn .menu a:hover{
  background-color: #5B92FB;
  color: #fff;
}