These are the original 3D stencils for iPhone micro-bga reballing. This set is a long time classic favorite for many students. The chip will sit fully within an etched pocket on the back of the stencil.
The square holes design makes it easier to take out the formed solder balls.
This 3D stencil is easy to use. This 3D stencil is thicker than ordinary stencils in the market. There is less tendency of these stencils to bend with heat and become deformed.