37 CFR 1.943 - Requirements of responses, written comments, and briefs in inter partes reexamination.
(a) The form of responses, written comments, briefs, appendices, and other papers must be in accordance with the requirements of § 1.52.
(b) Responses by the patent owner and written comments by the third party requester shall not exceed 50 pages in length, excluding amendments, appendices of claims, and reference materials such as prior art references.
(c) Appellant's briefs filed by the patent owner and the third party requester shall not exceed thirty pages or 14,000 words in length, excluding appendices of claims and reference materials such as prior art references. All other briefs filed by any party shall not exceed fifteen pages in length or 7,000 words. If the page limit for any brief is exceeded, a certificate is required stating the number of words contained in the brief.