The master file neither of you can read

A supplier can tell FDA things about its own manufacturing process that it will never tell the company buying from it. 21 CFR 814.20(c) is the provision that makes this ordinary: information in a master file submitted by someone other than the applicant is not considered part of that applicant’s PMA unless the person who submitted it — not the applicant — authorizes the reference in a record filed with FDA. The device manufacturer never has to see the file to benefit from it. Under FDA’s device master file practice, the same mechanism reaches 510(k)s and IDEs as well, not PMAs alone.

A letter, not a look

The document that crosses from supplier to manufacturer is a Letter of Authorization, filed with FDA, naming the master file and permitting FDA to consult it when reviewing the manufacturer’s own submission. The letter goes to FDA. It does not carry the file’s contents to the manufacturer, and by design it is not supposed to — the reason a supplier files a master file instead of handing process details directly to a customer is to let FDA evaluate the process without the customer ever reading it. FDA reviews the file. The company whose clearance depends on it does not.

Confidential by the same rule as everything else

A master file gets no special secrecy standard of its own. What a holder marks as trade secret or confidential commercial information inside it is protected under 21 CFR 20.61, the same provision that shields any submission’s confidential content from public disclosure — and if a master file goes five years without being referenced by anyone, FDA returns it to the person who filed it. Nothing about a master file’s existence, its holder, or what it says becomes a public fact on its own.

On the drug side, that absence has an exception. CDER publishes a Drug Master File list — number, status, type, holder, subject — updated every quarter, under its own regulation at 21 CFR 314.420. FDA’s device master file guidance for CDRH names no equivalent. There is no public place to check whether a given supplier holds one at all.

What that means for a portfolio read

A competitor’s 510(k) or PMA can rest, in part, on a component or process a master file describes — and nothing in the clearance record, in openFDA, or in FDA Radar’s own ingestion of either says so. The record shows an outcome. It does not show what it was built on. Whether a specific supplier relationship, disclosed or not, changes how you read a specific competitor’s clearance is a judgment for a regulatory professional working from what that supplier and that manufacturer are actually willing to say — not a conclusion a public record, or this post, can reach for you. This is regulatory intelligence and method, never regulatory advice about a specific device’s manufacturing chain.