Key Features: Genuine E3D Parts A handy little spring to pop onto timing belts that helps keep tension Tested these with GT2 Belts, T 2.5 mm and T5 belts Will probably suit any belt that is 6mm wide A handy little spring to pop onto timing belts that keep things tight and tensioned easily. We' ve tested these with GT2 Belts, T 2.5 mm and T5 belts. Will probably suit any belt that is 6mm wide. Item Specifics 1 - 2GT Tensioning Spring