Simplicity Nasal CPAP Mask
The Simplicity is probably the easiest nasal cpap mask to wear. It has very minimal contact with the face and no hard plastic near the face at all. There is no forehead piece, just straps. It comes in 2 sizes (small & medium). It may not work well for a person who may need a large size nasal mask.
It takes up very little space and is, therefore, a good travel mask.
I used it in my titration study (7+ years ago) and still keep one on hand as well as one in my cpap travel bag.
See cpap.com for an image of this mask.