I bought this Cover for my Marshall JMP reissue 1987x 50w Plexi head. My head was standing in the rehearsal room and I found out that the air always was a bit damp. I saw that the metal parts inside of the amp started to tarnish a bit, what was horrible. So I bought the amp cover for it. It is made out of a synthetic material. Water has no chance to get trough the material, which was important to me. And it worked! The condition of the metal parts hasn't got worse since the day, I started to use this cover. So I'm really happy with this product.