Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Manufacturing design error

The product is excellent for a couple of weeks. Then the little nib of crayon or whatever is used up and there is no way to make it extend out to use any more. It's encased in plastic and can't be sharpened. There seems to be a serious defect in design here. I wouldn't buy it again unless there's some way to screw the contents further down the tube.