This paper presents a comprehensive study on the quality and reliability of commercially available medium voltage surge arresters, with particular emphasis on their electrical performance and structural degradation under aging conditions. Samples from four manufacturers were subjected to 8/20 μs aging impulses and accelerated durability tests. Electrical analysis revealed that some products exhibited excessively high residual voltages (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns