Can't modify featured image size on blog post display

Hi There,

For some reason I’m not able to modify the featured image on ALB blog post display using Small Author, Small Preview Pic. Using the code below, however the image still appears as 81px by 81px

.small-preview {

width: 175px;
height: 150px;
overflow: hidden;
border-radius: 4px;
float: left;

}