Some vehicles such as Ford Windstar mini van, Ford Econoline van, Ford Explorer, new Chevy/GMC pickups, Ford Ranger pickup, and Mazda pickups have a moulding with a piece of metal inside. If you cut into the moulding the metal insert makes it difficult to cut. Also, many encapsulated glasses have a very dense encapsulation material that is difficult to cut. The BFS1421 and BFS1422 are designed to hold the blade below the moulding and prevent the blade from cutting into the moulding. A permanently-attached, lubricated nylon spacer lets the blade move easily back and forth while holding the blade under the lower lip of the moulding or encapsulation. Made of a specially-formulated steel that is hardened and then tempered using a cold molecular-aligning process. This makes the blades very flexible. Each blade will easily remove over 50 windshields when used according to directions. Made in USA.