TDK and Maxell. But what about??

What about Radio Shack MPX premium metal cassettes??? I think they sound pretty good. I bought some 2 years ago when they were being discontinued. Seems like everything else I have ever heard from Radio Shack has been sub-good fidelity in the past but these seem to be pretty decent. What do you think? And who makes their tapes??????
I wasn't too crazy with the Radio Shack Type 4 Metals myself.I couldn't push the headroom on them so much.The very best ever made were the TDK MAK-G if you could ever find them.The 90 Minute Tape sold for almost $10.00 each if memory serves me right.But they had this huge headroom befor 3 percent T.H.D. set in making them a prime candidate for live recordings.
I was able to almost push them to +5 to +7 DB over Zero which is unheard of from any tape ever made in the 1.75 IPS format on cassete.