button widths

I've created a simple button in the GP theme and applied some CSS, however when I apply a px width in the CSS nothing happens. I have 3 buttons on the home page, set to the same exact class. RESEARCH & DEVELOPMENT, MANUFACTURING, PRODUCT DESIGN. I want the Manufacturing & Product Design buttons to be the same width size as the Research & Development button. Website is attached below.

This is the element code I'm using:

<p style="text-align: center; font-family: Roboto,Helvetica,Arial,Lucida,sans-serif; font-size: 18px; color: #0f517d; letter-spacing: 2px; font-weight: 100;"><span style="font-family: Roboto; font-weight: 300;">MANUFACTURING <i class="fas fa-long-arrow-alt-right"></i></span></p>

Here's the CSS I'm using

.rdbutton {
border: 1px solid #59595b;
background: -webkit-gradient(linear, left top, left bottom, from(#002f4d), to(#001726));
background: -webkit-linear-gradient(top, #002f4d, #001726);
background: -moz-linear-gradient(top, #002f4d, #001726);
background: -ms-linear-gradient(top, #002f4d, #001726);
background: -o-linear-gradient(top, #002f4d, #001726);
background-image: -ms-linear-gradient(top, #002f4d 0%, #001726 100%);
color: #a8a8a8;
font-size: 17px;
font-family: lato, serif;text-decoration: none;
vertical-align: middle;
padding:20px 20px 20px 20px;
height:0px;
width:366px;
}