This is a KOSSEL mod to hold an E3D Hot End and magnetic arms with 10mm spheres. It's designed to be used either with H or C carriages, but I recommend C carriages because the plastic part will activate the end stop and will behave better (in my experience). You need to buy 10mm diameter ball bearings (check the specific material closely, not all of them are magnetic), and 10mm diameter by 10mm or 15mm height neodymium magnetic discs. You can include spacers to leave the E3D leveled with the plate (I might design them later...) http://youtu.be/uRZE-9WTdH8