The dimension -6 proton decay operators are q q q ℓ ℓ / Λ Λ 2 , d c u c u c e c / Λ Λ 2 , e c ¯ ¯ u c ¯ ¯ q q / Λ Λ 2 , and d c ¯ ¯ u c ¯ ¯ q ℓ ℓ / Λ Λ 2 , where Λ Λ is the cutoff scale for the Standard Model. All of these operators violate both baryon number (B) and lepton number (L) conservation but not the combination B − L.