Here's a pic of an old EF L series 100-300 1:5.6 zoom lens that a pro friend handed down to me. Does anyone know what tripod mount ring I need for this lens? My friend told me she didn't use a tripod mount with it and mostly shot hand-held, but on my Rebel 300D it feels very unbalanced and sometimes the rig just slips out of alignment as I'm adjusting it.
. Canon manufactures two tripod collars (in two colors
). Details can be found at: 
)
