At Simply Solar we strive to do a quality installation because this is critical for the long term performance of your system.  For example the panels are connected with a 4mm solar cable and MC4 connectors.  These are available locally and made in China however we are using connectors and cable from   http://www.multi-contact.com/ which is a top-of-the-line manufacturer in Germany.  The fasteners on our roof mounting systems are extruded aluminum, nut are stainless nylock, etc.  Our installs are preceeded by a PV simulation for your specific location and needs.  This report is provided to you without charge.