19 C.F.R. § 10.520
A cotton or man-made fiber apparel good described in § 10.521 of this subpart that does not qualify as an originating good under § 10.531 of this subpart may nevertheless be entitled to preferential tariff treatment under the SFTA under an applicable tariff preference level (TPL). To make a TPL claim, the importer must include on the entry summary, or equivalent documentation, the applicable tariff item in Chapter 99 of the HTSUS (9910.61.01 through 9910.61.89) and the applicable subheading in Chapter 61 or 62 of the HTSUS under which each non-originating cotton or man-made fiber apparel good is classified. For TPL goods, the letters "SG" must be inserted as a prefix to the applicable HTSUS 9910 tariff item when the entry is filed. The importer must also submit a certificate of eligibility as set forth in § 10.522 of this subpart.
19 C.F.R. §10.520