270W Polycrystalline solar panel which uses 156mm has advantages as follow: Current classification reduce Mismatch loss Low hot spot temperature higher safety performance Low power loss under shadows 5BB reduce the current heat loss of the battery inside the module,beautiful apperance,more suitable for roof installation Regarding the quality issues,You are entitled to a replacement or refund for a major failure and for compensation for any other reasonably foreseeable loss or damage. You are also entitled to have the goods repaired or replaced if the goods fail to be of acceptable quality.