<div class="row row_1" id="radiobtn">
<label for="model1">
<div class="details radiobtn">
<p>йуйц</p>
</div>
<input id="model1" type="radio" name="model" class="inv" />
</label>
.row input[type="radio"]:checked + .details{
border: 2px solid #08c;
}