The Society of the Plastics Industry, or SPI, establishes standards for the United States plastics industry. Among the SPI standards is one defining the degree of finish. The SPI standards specify 12 grades of mold finish ranging from mirror-perfect to a light texture.

SPI grades A-1, A-2 and A-3 are high ultra high gloss finishes buffed with different grades of fine diamond compound. They are specified to make plastic mirrors and lenses

SPI grades B-1, B-2 and B-3 specify semi-gloss finishes with some sheen. These finishes are last step before the diamond buffed "A Grades" and are achieved by using very fine wet and dry sand papers. They are specified to make plastic parts that are shiny but not transparent.

The SPI's grades C-1, C-2 and C-3 specify non reflective finishes. These finishes are the basics utilitarian finishes. Either the first step to glossier finishes or interior finish of plastic parts where not visible to the end user. Fine polishing stones are used to achieve these finishes.

SPI grades D-1, D-2, D-3 specify dull, matte finishes. These finishes are usually accomplished by the use of various mediums with the vapor blast process and are used where a matte or dull finish is aesthetically preferable.