American Grip ears and corners. make a 6x 8x 12x overhead/butterfly frame.  Classic set and very common.  build any size frame with 1x1 aluminum frame.  can be purchased at any metal shop.  build 6x6 , 8x8, 12x12 sizes or any size you want.  hang ultra bounce or solids or grids, silks and many many different kinds of diffusion.