Landpride brush mower grease fitting ?

[gaswamp]

I am having trouble locating the appropriatte size grease fitting for a Landpride rcr 1560 mower on the U-joints. Anybody know the correct size?

 

[RickB]

I am having trouble locating the appropriatte size grease fitting for a Landpride rcr 1560 mower on the U-joints. Anybody know the correct size?

It is probably 6mm. 6mm is a little smaller than 1/4"-28.