1/4" NAP (Thickness): This roller sleeve is used for semi gloss or high gloss finishes where a smooth finish is desired. This includes paints and polyurethanes. Select a lint-free sleeve for these applications. Generally for use on doors and other decorative trim, but can be used on walls when using gloss finishes.
MOHAIR: This roller sleeve is primarily for use with high gloss or polyurethanes. Greatly reduces the "orange peel" look. Also works well for glazes when complete walls are to be glazed.
3/8" NAP: Best choice for wall painting where a quality finish is desired. This roller sleeve will hold enough paint to cover walls thoroughly with limited roller "stipple". Stay with lint-free sleeves here too.
1/2: NAP: This roller sleeve should be used where coverage is the primary objective. It will hold and apply a lot of paint with each "dip". There will be significant "stipple" in the finish and is not a good choice for residential work. Very good choice for commercial, production work. It is also the best choice if painting lightly textured ceilings (previously sand painted, etc.)
3/4" and 1" NAP: These sleeves are referred to as "bulldozers" in the industry. They hold and apply large quantities of paint and should be used only for commercial applications where coverage is more important than the esthetics of the finish. The only time to consider these in a residential application is when painting heavily textured walls or ceilings.