The STA120-12 modules are composed of 36 multicrystalline silicon solar cells of similar performance, interconnected in series to obtain the 12 Volt output.

A heavy-duty anodized aluminium frame provides strength and convenient mounting access. For each 18 cells series strings, one bypass diode is installed. Cells are laminated between high transmissivity, low-iron, 3mm tempered glass and sheet of tedlar-polyeaster-tedlar (TPT) material by two sheets of ethylene Vinyl acetate (EVA). This protects against moisture penetrating into the module.