In plain English
FAR 52.211-3, Availability of Specifications Not Listed in the GSA Index of Federal Specifications, Standards and Commercial Item Descriptions, is a contract clause prescribed at FAR 11.204(c), most recently dated June 1988. The complete official text is reproduced below, verbatim, from GSA's published FAR source files.
Its text contains no sentence requiring insertion into subcontracts; see the flowdown section below for what that does and does not mean.
Does it flow down to subcontracts?
No flowdown mandate found in the clause text
We scanned the full clause text and found no sentence directing the contractor to insert this clause into subcontracts. That is a statement about the text, not legal advice: a prime contractor may still flow terms down contractually, an agency supplement (DFARS, VAAR, …) may add requirements, and clauses listed below (if any) may order this clause into subcontracts from the outside.
Where it's prescribed
As prescribed in 11.204(c), insert a provision substantially the same as the following:
Prescribing reference: FAR 11.204(c).
The official text, verbatim
As prescribed in 11.204(c), insert a provision substantially the same as the following:
Availability of Specifications Not Listed in the GSA Index of Federal Specifications, Standards and Commercial Item Descriptions (June 1988)
The specifications cited in this solicitation may be obtained from:
(Activity) address) ________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
(Telephone number) _________________________________
(Person to be contacted) ______________________________
The request should identify the solicitation number and the specification requested by date, title, and number, as cited in the solicitation.
(End of clause)