Fig. 3
From: 3D Printed frames to enable reuse and improve the fit of N95 and KN95 respirators
Attachment of the head band to a mask frame. a A knot is tied at the end of each band and the band is then slid into and locked in place using the PLA slot. b Mask frame with bands. c Clip attachment of the frame to the bands on the 3M N95 Model 1860 respirator