KF40 blank flange, stainless steel 304.

https://www.allectra.com/products/431-kf40-b/

Position proposed, between T11.MQNEG008=157 and T11.MBXHF010 :

https://panoramas.cern.ch/viewer?fov=90.00&id=56913956&lat=23.93&lon=209.93