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Before your company is ready to sell products or services to the government, the first step is identifying and refining your product or service niche. Making sure your offering aligns with the correct Special Item Numbers (SINs) not only strengthens your GSA Schedule contract proposal but also helps you stand out to federal buyers and connect with the right contract opportunities.
The Multiple Award Schedule (MAS) Program covers a broad range of products and services, and SINs are an essential part of the MAS Solicitation. Throughout the course of this blog, we will cover what a SIN is, why it is important, and how to determine the right SIN for your business.
What Are Special Item Numbers (SINs)?
The GSA Schedule is organized by large categories, subcategories, and SINs that have corresponding North American Industry Classification System (NAICS) Codes. There are 12 large categories corresponding to specific industries. Specific products and service subcategories within a given large category have an associated SIN that defines and further narrows down your proposed pricelist. The full list of large categories is as follows:
- Office Management
- Facilities
- Furniture & Furnishings
- Human Capital
- Industrial Products and Services
- Information Technology
- Miscellaneous
- Professional Services
- Scientific management and solutions
- Security and protection
- Transportation and logistics services
- Travel
SINs vs. North American Industry Classification System (NAICS) Codes
SINs are different from NAICS Codes. Developed by the Office of Management and Budget (OMB), NAICS Codes are the standard used by federal statistical agencies in classifying business establishments for the purpose of collecting, analyzing, and publishing statistical data related to the U.S. business economy. NAICS Codes are also useful to determine if your organization qualifies as a small business and is a useful tool to identify contracting opportunities for your business. SINs are specific to the MAS Solicitation and allow businesses to potentially grow their reach to government buyers within the public sphere.
Significant SIN Changes in Solicitation 47QSMD20R0001 Refresh #27
Solicitation Refresh #27 was released in June 2025, and it includes significant changes regarding SINs. The following SINs have been retired:
- 332439MLB - Mail Lock Boxes
- 337127P - International Packaged Furniture
- 339113G – Gloves
- 339113P - Packaged Healthcare Furniture
- 339930 - Doll, Toy and Game Manufacturing
- 339992 - Sounds of Music
- 339999A - Awards
- 339999ASB - Awards (SBSA)
- 511130 - Books and Pamphlets
- 532289 - Furniture Rental and Leasing
It's important to note that GSA has recently released Refresh #28, created due to a system issue with Refresh #27. There are no additional changes in Refresh #28. The most up to date version of the MAS Solicitation refresh can be found on SAM.gov. GSA is consistently monitoring the market to add new products and services, and new refreshes could result in SINs being added or retired.
Why are SINs Important?
There are a multitude of products and services that your business can sell to the government, and government buyers are able to view all opportunities under any corresponding SIN in GSA eBuy. It’s important to market your products or services under an accurate SIN to ensure that your business is being notified and taking advantage of all potential opportunities.
The GSA eBuy system is an electronic Request for Quote (RFQ) or Request for Proposal (RFP) system, enabling government buyers to request information and price quotes for large purchases of your products or services.
Without the correct SIN for your products or services, your business may struggle to gain visibility with government buyers, which can negatively impact your MAS contract. Choosing the most specific SIN available helps position your business for success and maximizes your chances of attracting interest from government buyers.
How Do I Determine My Special Item Number (SIN)?
The full list of SINs currently available through the MAS program can be found on the SIN lookup table as found on the “Multiple Award Schedule” page on GSA's website. Information on the lookup table includes the large categories, subcategories, SIN, NAICS, SIN title, SIN description, and SIN-specific resources. The lookup table also allows you to see eligible contractors within a given SIN, making it a helpful resource for identifying potential competitors and gauging how saturated the market is.
It is important to be aware of specific requirements for certain SINs to avoid delays or setbacks in securing your MAS contract. For example, SIN 54151HACS under large category F, Information Technology has a strict set of requirements. Contractors wanting to sell services under this SIN must provide two past project descriptions completed within the past two years or ongoing with at least one year of work on the project. Contractors must also comply with certain National Institute Standards and Technology (NIST) requirements and complete an oral technical evaluation conducted by a Technical Evaluation Board (TEB). Specific requirements for a given SIN can be found in the resources tab on the SIN lookup table.
When determining which SIN is right for your company’s offering, make sure the SIN title and description accurately reflects the products and/or services you provide. If you are unable to provide substantial evidence as to how your products and/or services relate to a given SIN, your MAS proposal could be at risk for rejection.
Can I Modify SINs on my GSA Schedule?
As your business evolves under a GSA MAS contract, you may choose to expand or narrow the range of products and services you offer. After your contract is awarded, you can add or remove SINs as your company’s needs change. When adding SINs to your contract, it is required that your product or service has been sold commercially. You will need to provide a past project narrative and an example of the sale verification, like an invoice or contract (Adding or deleting SINs from your contract is just one example of the modifications your company can make after the award. Our team at Winvale is here to help with any modifications your business needs throughout the life of your contract.
Navigating SINs in the Multiple Award Schedule Program
With so many specific SINs to choose from, it can feel overwhelming to find the one that best fits your company’s needs. Becoming familiar with the SINs that closely align with your offerings is the first step toward choosing the right one to gain exposure in the government marketplace. If you have questions about SINs or where to begin with a GSA MAS contract, the Winvale team is here to help!
