I would say "My shirt is of good quality" :)

Your reply to Kadiga comes across as rude. It's also nice to thank people who answer your questions, even if you did not find the answer helpful. On the issue itself, I would say that both your options are wrong. These would be good: "My shirt is of a good quality" (formal) "I have a good-quality shirt" (neutral) This is also probably common : "My shirt is good quality". I don't know if this is wrong, or just informal but acceptable. In modern UK slang, people say "My shirt is quality", to mean, "My shirt is of a high quality".