Not hard anodized other than that they are well made - Mitchell Defense Enhanced A5 Length Buffer Tube

The tube is coated with something other than hard anodizing. It was nice looking on the outside but the inside bottom of the tube was raw aluminum where the end of the steel spring seats. I worry it will wear through over time so I sent it back. The owner of Mitchell defense sent a new one to replace it. The new one. looked like it was coated but it was not hard and just wiped off when I installed the spring into it. Sent that back too. Bought a different brand.The tube was well made other than that. They need to get their tubes anodized rather than whatever they are coating them with.