VEVOR 6"x 6" Post Base, 1Pcs Stainless Steel Adjustable Post Anchor Bracket(Internal 5.9 x 5.5"), Adjustable Post Base for Pavilion Deck Porch Handrail Railing Support Decorative Anchor Plate

The product description states this post base is made of 0.07 inch thick stainless steel with a brushed finish to resist corrosion and rust, ensuring durability for outdoor use.

Yes, all necessary installation accessories are included, according to the product description. The package comes with stainless steel expansion screws, hex bolts, nuts, self-tapping screws, wrenches, and a braided cloth for a seamless installation experience.

The product description doesn't mention anything about maintenance. However, it states that the post base is made of stainless steel with a brushed finish, which helps resist corrosion and rust.

Based on the product description, it is suitable for installation on various surfaces, but it does not specify whether it can be used on uneven surfaces.

The 6 x 6 Post Base is not available in 5.5" x 5.5".