Use this replacement 10mm pen tube if you have damaged the pen tubes that came with your pen kit.
These pen tubes are 10" (approx 25cm) long and come in a pack of 6. They should be cut to the correct length using a fine saw.
Please note, the tube fits a 10mm drilled hole. The tube diameter is a bit smaller than 10mm to fit the drilled hole and have space for a glue layer.
After cutting, they should be squared using a barrel trimming set.