They were referred to us by the manufacturer of our plotter- HP for services, when it was not working. We call and they send someone right away to work on it and figure out what parts are needed to be ordered and replaced. Once we got the shipment, we called her (the technician) directly to install them. It’s better to contact this company directly, to prevent third party involvement that would mark up the charges. Now that we know that, we would not make that mistake again.