Uxcell PLA Filament Refills for 3D Printing Pen 10inch Length 40pcs Are there any advantages of the product? There is no need to worry about shrinkage when cooling easy to use no peculiar smell during printing. The printed model has good hardness and is durable as a structural part. The melting point is low the flow is fast and it is not easy to block the nozzle. How to use it? Put the refill filament into the feed opening at the end of the 3D printing pen and the filament should be against the front end. Then press the discharging button on the side of the charging port and wait for the 3D printing pen to heat up the filament before creating.