Genuine original Canon part. BRAND NEW, NEVER BEEN USED. 

It's compatible with Canon Lens:

EF 400mm 1:4.0 DO IS USM Mark I, 

EF400mm F4 DO IS II USM, Mark II 

EF 200 mm F2.0L IS USM

EF 300 mm F2.8L IS II USM

EF 200-400 mm F4L IS USM Extender 1.4x