Flags are great when used for promotional events or as a more permanent display/ feature. There is a variety of materials that can be used. Either with a more open or closed weave depending on the applications location and desired effect. Depending on the printer that you have, you may be able to print double sided but generally these are printed single sided and if a doubled sided flag is required are then stitched together. Some printers support the use of a mesh printing kit, which enables a better print quality onto open-weave textiles and produces deeper colours.
You will need