What cut of beef for guydon?

I was wondering if anybody knew what cut of beef Yoshinoya and Matsuya use for their gyudon. I've tried numerous cuts and none have come close enough to mimicking their style. I would assume that they use a meat slicer to get the beef that thin also.

sorry, for the damn title.
ok, on to business:
you don`t live in japan, aren`t you?
because if yes. thean you just have to go to the next supermarket and look for 薄切りもも（牛肉）
if you don`t live in japan, than it would be a little bit difficult to get your meat that thin sliced. you can ask the next butcher, but usually they don`t get it that thin.
when I was living in Germany I used to go to an korean butcher. they do it.
so maybe you should look for such a shop. too. korean, japanese, chinese...what ever in this category..
good luck!

i have found a way to cut the beef really nice and thin but its kinda hard to cut and you have to be really careful....all you have to do is freeze it then cut it...try it out...it turns out really super thin...let me know if this works for you

Here in Seattle, I shop at a store called Uwajimaya. They have both very thin sliced Beef Sirloin and Beef Shortribs. I use these to make Gyudon, Sukiyaki, Bulgogi, and Shabu Shabu (though still too thick for Shabu Shabu).

This recipe site tells you to use beef sirloin:

http://www.recipezaar.com/Japanese-Beef-and-Rice-Bowl-G...

Try to see if there are some Japanese grocery store in Minnesota.

I found one in Minneapolis:

United Noodles
2015 E 24th Street
Minneapolis, MN 55404
Monday to Saturday: 9am - 7pm, Sunday: 9am - 6pm
Tel: 612-721-6677 Fax: 612-721-2019
Email: info [at] unitednoodles [dot] com
Website

http://www.unitednoodles.com/catalog2/index.php