Tips are replaceable and reversible (each tip is dual sided. There are instructions in the package on how to replace the nibs. The colors are really thick and seems to be plenty of ink in these markers. The bag is of good quality seems cheap at first but then you realize how sturdy the stitching is and you rethink it. Jazza from Youtube put these markers right up against the best of the best (copic, windsor, crayola, etc) and placed them in the top 10 markers on the market so I had to give them a try. Extremely glad I did. The value is there, and the quality is there. The tips are of high quality and the inks are colorful. I am an intermediate user of markers (graphic designer) and I will be using these as long as the company keeps the pricepoint and quality. Copic lost a customer today.