Fencing - Vinyl Fencing Oz-Post offers two models that are suitable for Vinyl fencing, the P5-850 5" square and the P4-850 4" square. With both of these models the vinyl posts are inserted into the Oz-Post™ and fastened with screws. The added bonus to using Oz-Posts for your vinyl fence is that the housing of the Oz-Post (if left above the ground by a few inches) will protect the vinyl from getting damaged by lawn care equipment!