Dual filter face mask

Remodeled a face mask from grabcad by Silviu Stroe to accept the modular filters created by MrDWGraf.

Supports only required on the bottom of the filter screws.

3 Sizes with internal dimensions top to bottom (nose to jaw): Large = 121mm, Medium = 112mm, Small = 99mm.

Edit: fixed inverted thread pattern on the left side