Fig. 4
From: 3D Printed frames to enable reuse and improve the fit of N95 and KN95 respirators
Properly donned mask frames and respirators on three different volunteers. a A 3M 1860 N95 domed healthcare respirator, b a 3M 8210 N95 domed industrial respirator (note a valve-less version of the model is used in healthcare settings but was not always available for testing due to widespread respirator shortages), c a Kimberly Clark duckbill, and d a KN95 flat-fold respirator. The bands should be sufficiently tight and the nosepiece manipulated to achieve a good seal