Seem to work well
I expected them to be a little softer/more flexible silicone molds, but they are sturdy and comfortable as-is.  They work best with a tri-fold type mask, because they have little hangers on either side to hook into place in those....but they can still be used with other types of masks and stay in place if your mask fits correctly.  It does help with breathing and vocal projection by not having your mask right up against your mouth.
Rating: 4 stars