Supplier tiers explained: OEM, Tier 1, Tier 2, Tier 3 and beyond

Written by Matt Barden, founder of Industrial Marketing. We market companies on every rung of this ladder, and it's the first thing we work out with a new client: who they sell to, and what that buyer checks. Every company named in an example on this page is invented.

Checked October 2026.

The difference is distance from the OEM. A Tier 1 supplier contracts directly with the OEM and usually carries design or program responsibility for a system. A Tier 2 supplier sells components to Tier 1 and rarely speaks with the OEM's buyer, though the OEM's engineers often specify its part. A Tier 3 supplier makes parts or runs a process for Tier 2 and is judged on capability, quality and quote speed.

Distance changes what the buyer is buying. Close to the OEM, the buyer is trusting you with a program: launch dates, engineering changes and a quality system that holds up in an audit. Further down, the buyer is filling a line on a bill of materials: can you make this part, to this print, by this date, at this price.

It also changes how wide your customer list runs. A Tier 1 may build its year around a few OEM programs. A Tier 3 job shop may quote for dozens of Tier 1 and Tier 2 buyers across several markets in the same month.

Long supply chains run past Tier 3 to the companies that make the material itself. Foundries pour castings. Forges make forgings. Mills roll bar, plate, sheet and wire. Service centers cut it and stock it. Powder makers supply additive and sintering lines.

These suppliers sell by grade, form and size range. The grade is usually set by an OEM materials engineer long before a Tier 2 or Tier 3 buyer places the order, so a forge can be the furthest company from the finished product and the closest to the original spec. Its buyers check grades, size ranges, certifications and test reports.

Numbering past Tier 3 varies by industry and by company. One chain calls a forge Tier 4. Another calls it a raw-material supplier and stops counting.

OEM is the general word for the company that sells the finished product. Prime is the defense and aerospace word for the company that holds the main contract. Automotive made the tier numbers common; aerospace, medical and energy now use them too.

The words blur in practice. A machine builder is an OEM to its own customers and a buyer to its Tier 1s. A distributor may call every brand it carries an OEM. When a buyer says OEM, ask whose finished product they mean.

A tier describes one customer relationship. It doesn't describe the whole company. The same machine shop can be Tier 3 to an aerospace Tier 1 on one job and Tier 1 to a packaging machine builder on the next, when it ships a finished assembly the builder bolts straight in.

That's why most companies sit on two rungs at once, and why the rung matters for marketing. Each rung has a different buyer checking different things. A page written for an OEM's program team loses the Tier 2 buyer who came to compare lead times.

Here is one invented aerospace chain, rung by rung. Anvil Point Forge forges aluminum blanks to a grade the aircraft maker's materials engineers chose. Twin Ledge Precision machines the blanks into fittings to a Tier 2 print. Quarry Hill Hydraulics builds the fittings into a hydraulic manifold. Saltmarsh Landing Systems builds the manifold into a landing-gear system and delivers it to the aircraft maker.

The part climbs four rungs. The spec travels down the same four: the alloy and heat-treat call-outs set at the top pass through every drawing until they reach the forge. Each company sells to the one above it, and each one is checked against a spec written further up.

Distributors, testing labs, engineering firms and automation integrators sit beside the ladder and sell into every rung. Their buyers are the plant, quality and engineering managers at each tier.

A distributor sells cutting tools to a Tier 3 shop and spare parts to an OEM's field service team. A testing lab runs material tests for a forge and validation tests for a device OEM. An integrator builds a robotic cell for a Tier 2 molder. None of them carries a tier number. Each still needs to know its customer's rung, because the rung decides what the buyer checks.