Surgical mask backstrap 口罩帶扣

thingiverse

Surgical Mask Backstrap In the recent COVID-19 outbreak, wearing a surgical mask became essential. Some surgical masks may be too large for women or children. This backstrap tightens the mask and improves its fit, reducing strain on the ear loops. If the backstrap is too short, you can stretch it to the right length. The strap will return to its original shape when heated to 70 degrees Fahrenheit. February 24, 2020 A surgical mask backstrap measuring 8 cm has 3 and a half wavelengths. A surgical mask backstrap measuring 11 cm has five and a half wavelengths. A surgical mask backstrap measuring 14 cm has seven and a half wavelengths. A surgical mask backstrap measuring 17 cm has nine and a half wavelengths.