Vinyl Fence POST CAP: 5" BALL CAP (5 Inch) Dome Style ~ White Vinyl Fence Parts ~ Fits over a 5x5 vinyl fence post (sleeve style post). Vinyl fence material is PVC and will not rot or fade. Fits over a 5" x 5" vinyl fence post. Vinyl PVC will not fade or rot. Viny BALL CAP AKA Vinyl Fence Post Cap - "Dome Style" Can use on vinyl mailbox post as well if vinyl 5x5 post. WHITE Vinyl Post Cap -