From the reviews-
"Was concerned about the size as it wasn't listed anywhere, but they fit great on my 7/8" bars (bar ends I ordered were 7/8" and fit well)."
They will fit the 636.
A few cruisers have 1 inch diameter grips for a fatter look, and most other motorcycles use 7/8 inch diameter grips.
“…[Most] try to wring from the unknown the answers they have already shaped in their own minds...It has taken eighteen hundred years to come back to the skepticism, the level of practicality that was our daily frame of mind then..." From the 1985 The Vampire Lestat novel by Anne Rice