On　small-sized　Ni60Nb40　magnetron-sputtered　glassy　films　confined　by　frame,　we　experimentally　revealed　a　significant　size　effect　on　the　elastic　strain　limits　by　in　situ　transmission　electron　microscopy　observations.　Ni60Nb40　glassy　films　with　thicknesses　of　50,　100　and　200　nm　exhibit　elastic　strain　limits　of　6.5-6.6%,　4.7-4.9%　and　3.5-3.6%,　respectively.　No　effects　of　changing　length　or　width,　or　the　ratio　of　width　or　length　to　thickness　on　the　elastic　strain　limit　are　detected　in　the　studied　ranges.　The　size　effect　could　be　attributed　to　different　open　volumes　in　the　magnetron-sputtered　Ni60Nb40　films　with　various　thicknesses,　indicating　that　controlling　the　open　volumes　might　be　a　useful　way　to　tailor　the　properties　of　metallic　glassy　materials.　The　current　findings　provide　a　new　way　to　understand　the　tensile　deformation　behavior　of　metallic　glasses　and　supply　an　effective　approach　to　enhance　the　elastic　strain　limit　of　metallic　glasses.　(C)　2013　Acta　Materialia　Inc.　Published　by　Elsevier　Ltd.　All　rights　reserved.