An ethylene copolymer composition comprises: a first ethylene copolymer having a density of from 0.855 to 0.913 g/cm 3 , a molecular weight distribution, M w /M n of from 1.7 to 2.3, and a melt index, I 2 of from 0.1 to 20 g/10min; a second ethylene copolymer having a density of from 0.875 to 0.936 g/cm 3 , a molecular weight distribution, M w /M n of from 2.3 to 6.0, and a melt index, I 2 of from 0.3 to 100 g/10min; and optionally a third ethylene copolymer; where the first ethylene copolymer has more short chain branches per thousand carbon atoms than the second ethylene copolymer and the density of the second ethylene copolymer is equal to or higher than the density of the first ethylene copolymer. The ethylene copolymer composition has a density of from 0.865 to 0.913 g/cm 3 ; a melt index, I 2 of from 0.5 to 10 g/10min; and a fraction eluting at from 90 to 105°C, having an integrated area of greater than 4 weight percent in a CTREF analysis; and at least 0.0015 parts per million (ppm) of hafnium. Blown film made from the ethylene copolymer composition has a hot tack window (HTW) of at least 45°C (at a film thickness of about 2 mil) and a seal initiation temperature (SIT) of less than 95°C (at a film thickness of about 2 mil).