Micro-mesh
“These types of systems utilize a fine metallic mesh of either 304 SS or 316 SS supported by plastic, aluminum, sheet metal or metal extrusions. Support configuration, wire diameter and mesh size and quality are contributing factors to the efficiency of these units.”
Reviewed on this site: Valor, Gutterglove Pro, Gutterglove Ultra, LeafBlaster, MasterShield, LeafFilter, GutterDome.
Metal reverse curve
“This system has been around the longest, dating back to 1908. It uses a rounded nose sheet metal panel positioned over the gutter, usually held in place with plastic brackets or small metal clips depending on the diameter of the curve.”
Reviewed on this site: LeafGuard, K-Guard, The Original GutterGuard, Gutter Helmet, GutterMagic & GutterGuardian.
Reverse curve, waterfall type
“This system is made from re-cycled plastic and has one, two or three parallel slots relying on surface tension for its effectiveness.”
NCR rated this category 2 out of 5 overall; not reviewed individually on this site.
Slit / hole gutter covers
“These are usually constructed of re-cycled plastic containing thin parallel slits in the same configuration as the plastic reverse curve type. They usually are fitted to the inside of the gutter lip.”
Metal screens
“This is the most common type of gutter protection. It consists of expanded metal similar to chicken wire, only coarser. It usually comes in aluminum, but galvanized steel is still available.”
Plastic screens
“This type of screen uses different hole configurations and sizes. Round, diamond shaped, triangular and square are often seen in this group. Some have a synthetic mesh covering the holes.”
NCR reviewed Raindrop Gutter Guards and Genova Raingo Guards in this category; neither is in this site's archive yet.
Sponge / pipe cleaner
“This is not a cover, but an insert that is placed into the gutter. It comes in different densities including one that is in the shape of a huge pipe cleaner.”— NCR Consumer Advocacy Group, archived March 17, 2017