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GSA7 min readUpdated June 7, 2026

SIN 561621H: Harbor/Waterfront Security Products and Services and Professional Marine Security Services Guide for GSA MAS

A Refresh 32 guide to GSA MAS SIN 561621H, Harbor/Waterfront Security Products and Services and Professional Marine Security Services, including category fit, NAICS/PSC context, max order, TDR/OLM status, and offer preparation notes.

Built for
Contractors mapping offerings, pricing support, catalog files, labor categories, or Add SIN modifications to official GSA MAS scope
By the end
Understand where SIN 561621H fits and what evidence to prepare before using it in an offer or modification.
Field guide

When SIN 561621H fits

Scope fit
A close-looking SIN can still be wrong if the subcategory, PSC, NAICS, or deliverable story points elsewhere.
Signal
561621H Includes all types of harbor and waterfront security products, such as specialized surveillance equipment, professional marine security services, and training related to harbor/waterfront/marine security. ^^^^NOTE: Subject to Cooperative Purchasing
Response
Compare the buyer's requirement to the official SIN language before forcing the opportunity into a familiar lane.
Service proof
Product SINs can create TAA, letter-of-supply, CSA, EULA, or FCP Product File questions.
Signal
The SIN supports service work, labor categories, deliverables, and pricing support.
Response
Prepare labor category descriptions, service narratives, past performance, FCP Services Plus data, and pricing support.
Modification path
Adding a SIN can affect catalog files, service descriptions, pricing support, and buyer-facing records.
Signal
The contractor wants to add this SIN after award or adjust offerings tied to it.
Response
Use the Add SIN and Add Product/Labor Category modification pages to plan scope, price, and evidence changes.
Refresh 32

SIN 561621H quick facts

A compact view of the official SIN record from the user's Refresh 32 MAS offerings workbook.

Category
Security and Protection
Marine and Harbor
NAICS
561621
NAICS codes associated with the SIN in the workbook.
PSC
1940
Product Service Code mapped to the SIN.
Max order
$300,000
Ordering threshold for seeking additional price reductions.
Part 1

What SIN 561621H covers

561621H Includes all types of harbor and waterfront security products, such as specialized surveillance equipment, professional marine security services, and training related to harbor/waterfront/marine security. ^^^^NOTE: Subject to Cooperative Purchasing

The official record maps this SIN to NAICS 561621 and PSC 1940. Those codes are not the whole strategy, but they help explain how the offering is categorized for buyers and reviewers.

Part 2

How to prepare the offer story

For service-oriented SINs, keep the service description, labor categories, pricing support, and past-performance examples aligned. A reviewer should be able to see what work is being sold, who performs it, and why the rate story is defensible.

If the SIN is being added through eMod, write down what changes operationally: new scope, new pricing, new files, catalog impact, and who owns maintenance after approval.

Part 3

Buyer and SEO language to keep straight

Use the SIN number, title, category, and subcategory together: SIN 561621H - Harbor/Waterfront Security Products and Services and Professional Marine Security Services - Security and Protection - Marine and Harbor. That combination helps a buyer understand the lane quickly and helps the page avoid becoming a vague keyword page.

When writing capability language, explain the actual deliverables and evidence. Do not make the SIN carry the whole message by itself.

Examples

What this looks like in practice

Real-world checkHow to test SIN 561621H before building files

Start with the official title and description: Harbor/Waterfront Security Products and Services and Professional Marine Security Services sits under Security and Protection > Marine and Harbor. Then compare your actual commercial offering to that scope, not only to the NAICS code.

If the fit still looks strong, build the proof stack: offering description, pricing support, past performance or product support, and any SIN-specific files the current GSA instructions require.

  • Confirm scope language.
  • Check NAICS and PSC signals.
  • Match the pricing file to the offering type.
  • Keep the support package reviewer-friendly.

Frequently asked questions

Is SIN 561621H part of TDR?

The Refresh 32 workbook marks TDR as Y for this SIN. GSA states that TDR became mandatory across MAS SINs with Refresh 31, so contractors should still verify current contract reporting instructions in official GSA sources.

Can order-level materials be used with SIN 561621H?

The workbook marks OLM as Y. OLM treatment should always be verified against the current MAS solicitation, mass modifications, and contract-specific instructions.

Should I pick a SIN only because the NAICS matches?

No. NAICS helps, but SIN selection should be based on the actual offering, official SIN description, category/subcategory, pricing files, and buyer acquisition path.