SPI Mold Standards

The Plastics Industry Association (formerly known as the Society of Plastics Industry or SPI) mold standards play a crucial role in the field of plastic injection molding. These standards provide a set of guidelines and specifications that help ensure consistency, quality, and interoperability in the design and manufacturing of molds used in plastic injection molding processes. Experts here at The Toolroom are here to explain these standards and how they assist us in providing you the best possible product.

What are SPI Mold Standards?

The SPI Mold Standards are guidelines created by the SPI to assist The Toolroom and other manufacturers in the design and build of high-quality plastic components. The purpose of these standards is to ensure consistency across the industry while creating products that meet customer needs. These standards dictate everything from the mold design to the texture of the plastic surface.

Why are they important?

Adherence to SPI Mold Standards is crucial because they enable us to produce parts that are predictable in terms of dimensions, surface finish, and overall performance. This is essential because it saves time, reduces product failure rates, and provides excellent value to customers. Additionally, following the SPI Mold Standards allows The Toolroom to maintain our status as experts in the industry, a reputation we have worked hard for.

What are the benefits of SPI Mold Standards?

The most significant advantage of SPI Mold Standards is that they enable The Toolroom to produce the highest product that meets customer expectations. Because these standards provide a common language among manufacturers, it simplifies communication and eliminates misunderstandings. Also, since the SPI Mold Standards are widely recognized in the industry, The Toolroom is known for our commitment to excellence in product quality and consistency.

SPI Mold Standards Classes

The Plastics Industry Association/SPI mold standards categorized into five classifications to guide quotes and orders into uniform mold class types. These classifications primarily dictate the draft and design requirements of each parting surface. In addition to this, there are also guidelines for gate placement and part numbering that help manufacturers maintain compliance and make communication more efficient.


Production level



Class 101 Mold

More than 1,000,000Extremely highExtremely high production and fast cycle timesClass 101 molds are the priced the highest and made with the very best quality materials

Class 102 Mold

500,001 to 1,000,000Medium to highAppropriate for parts with abrasive materials and/or tight tolerancesClass 102 molds are high priced and made with high quality materials

Class 103 Mold

100,001 to 500,000MediumA very popular mold for low to medium production partsClass 103 molds are in the median price range

Class 104 Mold

501 to


LowGood for limited-production parts with non-abrasive materialsClass 104 molds fall into a low to median price range

Class 105 Mold

500 or lessVery lowPrototype only Class 105 molds are intentionally built as inexpensive o produce a very limited number of product prototypes

Each of these injection mold classifications has specific parameters. You can rely on The Toolroom for complete adherence to these mold standards and the entire classification spectrum.  For detailed information about SPI industry mold standards, click here.

The Toolroom provides our customers premier plastic injection molding services that adhere and surpass industry standards. Your choice of The Toolroom for your injection molding needs will be reflected in your bottom line with cost savings and the ability to concentrate on your business. The experts at The Toolroom utilized our advanced technology to deliver the highest quality product. With its state-of-the-art molding facility and injection molding processes, The Toolroom is the St. Louis region’s leading plastic injection molding service. Contact us today at (573) 437-4154.

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