Vista 1 in. H x 4 in W White Aluminum Base Plate Cover for 2.5 in. Post for Stair Railing Kit PB7746WT - The Home Depot

Highlights

2-piece construction simply snaps together around the base of the post
• Designed to hide the fasteners used to secure your 2.5 in. Vista aluminum post to your structure
• Powder coated aluminum construction matches Vista aluminum posts
• Covers around the 4 in. base plate accepting the Vista aluminum 2.5 in. posts
• Low-maintenance
• Easy to assemble