Synonyms: Phenol,4-bromo-2,5-dichloro-, O-ester with O-methyl ethylphosphonothioate; Phenol,4-bromo-2,5-dichlorophenyl-, O-ester with O-methyl ethylphosphonothioate; CelaK 41; K 41; K 41 (pesticide); O-(4-Bromo-2,5-dichlorophenyl) O-methylethylphosphonothioate; O-(4-Bromo-3,6-dichlorophenyl) O-methylethylphosphonothionate