Spider - PEI SpiderSheet with 3M adhesive - 280x355mmPEI (Polyetherimide) Sheet 280x355x0. 5mm (Ex. Ultimaker S5) SpiderSheet PEI (polyetherimide) is a strong, rigid plastic that withstands high temperatures. It is an ideal build surface for FFF 3D printers. To use, simply clamp on or stick on your heated build plate with our 3M 468MP adhesive sheets. When heated, the PEI sheet grabs onto your 3D print and doesn't let go, negating the need for a print raft. After printing, allow the sheet to cool before