An air filter element partially-fabricated on site wherein one or more wire frames are fastened to one another to form a structure substantially conforming to the dimensions of the original equipment manufacturer's filter housing. One or more of the wire frames are flexibly attached to each other end-to-end by flexible attachment means, allowing the assembled filter unit to be inserted into the filter housing one frame at a time, with the frame sections yet to be inserted folded or directed off to one side, thus bypassing space restrictions. Flexible attachment means may comprise spring connectors. Also disclosed is an end-cap affixed to or formed at one or both ends of the filter element. The end-caps may also contain printed material, such as text or pictures, which may include instructions for use, identifying labels or symbols, or the like.