<!DOCTYPE html>
<html>
<head>
<title>Title of the document</title>
<style>
.circleBase {
border-radius: 50%;
}
.circle1 {
width: 100px;
height: 100px;
background: #4bc475;
border: 1px solid #000;
}
.circle2 {
width: 150px;
height: 150px;
background: #a1a1a1;
border: 1px solid #000;
}
</style>
</head>
<body>
<div class="circleBase circle1"></div>
<div class="circleBase circle2"></div>
</body>
</html>