change No change On or before 12/31/2020 . 642. NEM salt Subchapter II of chapter 99 is amended by inserting in numerical sequence the following new heading: 9902.07.50 4-(4-Methylphenyl)-4-oxobutanoic acid - 4-ethylmorpholine (2:1) (CAS No. 171054–89–0) (provided for in subheading 2934.99.90) Free No change No change On or before 12/31/2020 . 643. 3M™ Fluorinert™ and performance fluid Subchapter II of chapter 99 is amended by inserting in numerical sequence the following new heading: 9902.07.51 C 1 -C 3 Perfluoroalkyl perfluoromorpholine (CAS No. 382–28–5) (provided for in subheading 2934.99.90) Free No change No change On or before 12/31/2020 . 644. Etridiazole Subchapter II of chapter 99 is amended by inserting in numerical sequence the following new heading: 9902.07.52 5-Ethoxy-3-(trichloromethyl)-1,2,4-thiadiazole (Etridiazole) (CAS No. 2593–15–9) (provided for in subheading 2934.99.90) Free No change No change On or before 12/31/2020 . 645. Pyroxasulfone technical Subchapter II of chapter 99 is amended by inserting in numerical sequence the following new heading: 9902.07.53 3-({[5-(Difluoromethoxy)-1-methyl-3-(trifluoromethyl)-1H-pyrazol-4-yl]methyl}sulfonyl)-5,5-dimethyl-4,5-dihydro-1,2-oxazole (Pyroxasulfone) (CAS No. 447399–55–5) (provided for in subheading 2934.99.90) 4.3% No change No change On or before 12/31/2020 . 646. Isatoic anhydride Subchapter II of chapter 99 is amended by inserting in numerical sequence the following new heading: 9902.07.54 2H-3,1-Benzoxazine-2,4(1H)-dione (Isatoic anhydride) (CAS No. 118–48–9) (provided for in subheading 2934.99.90) Free No change No change On or before 12/31/2020 . 647. Grazoprevir (MK-5172) Subchapter II of chapter 99 is amended by inserting in numerical sequence the following new heading: 9902.07.55 (1R,18R,20R,24S,27S)-N-{(1R,2S)-1-[(cyclopropylsulfonyl)carbamoyl]-2-vinylcyclopropyl}-7-methoxy-24-(2-methyl-2-propanyl)-22,25-dioxo-2,21-dioxa-4,11,23,26-tetraazapentacyclo [24.2.1. 03,12 .0 5,10 .0 18,20 ] nonacosa-3,5,7,9,11-pentaene-27-carboxamide