lens hood for 70-200mm f/2.8 non-IS

Lens barrel, where the hood attaches, not around the front element where the filters attach. Notice that neither of them are 77 mm. The lens barrel has to contain the lens element/group mountings, focussing rack, zooming rack, IS components, etc. Max. diameter (per Canon) of the IS is 86.2 mm, of the non-IS is 84.6 mm.

yea, i guess i figured that much right after i posted. still didnt know the IS was physically wider.

I don't know why my friend had this unusual idea on changing the hood. It seems no problem on the original hood, except he had a small crack on his hood. I'd prefer advising him to buy the original one simply.

Interesting enough. I didn't know the number of the hood refers to the diameter of the bayonet.