Focus Screen Information Online???

[HOUSCOUS]

Hi, forum. I am wondering where I could find information of each individual focus screen. Just wonder if there's any difference among the focus screen and the reason canon makes so many different one.

;););)

[Blue Deuce]

http://www.bhphotovideo.com/bnh/controller/home?O=search&A=search&Q=&ci=0&sb=ps&sq=desc&sortDrop=Relevance&ac=&bsi=&bhs=t&shs=focus+screens&at=Brand_Canon&basicSubmit=Submit+Query

[tcc]

http://www.focusingscreen.com/privacy.php