Nock_3d

hey guy i just start working on model for Arma also But my problem is i can see the hole after i put the model Glass [with texture alpha channel] on the model if i remove the glass mesh is look fine. is not just one hole have like 3-4 hole in the mesh. i am game Artist for Unreal 3 I know how model for game work but this problem i never see before in Unreal engine if you have any idea please help. thank you