If you buy Small wig (6-6.5inch, 5-6inch, 4-5inch and 3.5inch),
Small wigs are very difficut to make them.
It can be see Sewing Stitch mark and hair net. It is not a defective wig.
Wigs(Big size and small size) are light colors, hair net can show more.

And if the hair fix some parting, the hair net is not show.

If the hair parting is not fixing, the hair net and wig cap can show more.  
It is not a defective wig.