NOS, NOSR, OEM, Reproduction, & Aftermarket Parts, What to Know

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NOS = New Original Stock
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New, Never-Used parts from the Original manufacturer's initial inventory of Stock parts.
Other definitions include New Old Stock and New Obsolete Stock, however New Original Stock more aptly describes these parts. NOS parts are considered "Correct" in restorations and during high-level judging at car shows. These parts also maintain /increase the value on highly-prized/rarer cars.

- "NOS" does not include reproduction parts or "mint"/ "nice condition", "Like New" Parts removed from a car.

- Buyers Beware:  NOS Parts should be packaged in their original boxes or wrappings, in our case marked; "GM", "A/C Delco", "Delco", "Delco Electronics", and in some cases "PMD", "Harrison", "Fisher", or "Saginaw". The packaging should have the correct GM Part Number(s) which can typically be cross-referenced via a GM-Chevy Camaro, Pontiac Firebird Parts Manual, or other GM information sources. If you are unsure about a specific part, look at existing examples and compare them to originals. If you are really in doubt, Ask here on this site, Don't be shy.... there are many of us here, who have a lot of NOS goodies in our secret stashes and Minty examples on our car(s). Because the market for NOS parts has become so very profitable, there are plenty of scammers who've jumped into the game.

*Amongst the scams are:
- using actual GM packaging/labeling to re-package/re-label Reproduction and/or Used Parts... "NOS" Body Panels which are Reproduction/Knock-Off panels labeled with a "correct-looking" GM/Fisher sticker/decal. They are fairly simple to replicate with a decent printer, but you can spot fakes if you pay attention to details.
- Fake GM packaging of used and reproduction parts.
- "Bait and Switch"... Legitimate GM packaging with a used or knockoff part, or images of a NOS part in the Ad, but the seller switches it for a knock off part.

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NOSR = New Original Stock Replacement
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New, Never-Used GM parts from the Original Manufacturer, made to replace the original GM part. These parts differ in that they are "second-run" replacement parts, made by the original manufacturer for GM and sometimes with improvements, to replace an earlier GM part. These parts are sometimes referred to in the GM parts books as "Service Replacements". The parts books sometimes note that the old part number is "replaced/superseded by part number xxxxxxx". These parts usually look slightly different, but they function as good as, or better than the original part... sometimes these parts were the result of a GM TSB (Technical Service Bulletin) or a Recall.

Many Times these parts are called NOS by sellers. Sometimes they differ in appearance to the originals.

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OER = Original Equipment Reproductions
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These parts are usually licensed by the Original Manufacturer, (in our case, GM). These types of parts are typically made of high quality materials and to the original manufacturer's standards. Often, these are the same or better than the originals in quality and overall appearance, but not always. Some of these items can differ just slightly to noticably from the originals, so buyer beware if you are going for originality.

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OEM = Original Equipment Manufacturer
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The original manufacturer (or conglomerate corporation), who owns the patents to the original parts used by GM. OEM parts may differ quite a bit from the original design, but they function as intended. They are not always the best quality but are better than the next category.

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Aftermarket Replacement
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These are parts are supposed to fit and function the same as or better than the original design. Usually they are "good enough", but quality is often lacking. They are typically made in a foreign country & sometimes these parts are horrendously bad... #Beware the Evilpay Knockoffs!

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USED
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Used Parts are ANY parts that have been removed from a car, at any point in time, regardless of their condition or age... Preferably, Used GM parts in good condition are sometimes a better option than new aftermarket replacement parts... "Mint" and "Like New" are fair assessments of used parts in very good condition, however, as noted above, this does NOT include NOS, NORS/NOER Parts...
Used parts should be amongst the cheapest parts in most cases, but in some cases, used original parts get scarce as time passes, or in some instances, may be the only existing pieces left... rarity commands a premium.

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PERFORMANCE PARTS
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This describes an entire segment of parts designed to enhance performance, from "Factory" GM Performance Parts to Cheap Knockoff headers and intakes... Quality is all over the place. Obviously GM parts would have the best quality, in general, but some performance manufacturers take quality seriously, other take it as a guideline. NEVER expect performance parts to simply just "Bolt on & Go"... usually you need additional parts, a dremel, BFH, a torch, and tools you don't have and will never use again in your life.
DO YOUR HOMEWORK BEFORE YOU BUY THESE PARTS.