Single sided razor blade or GOOD knife, make a holder to guide a 90 deg cut, change blades oftenThanks for the info - I assume these have the ml markings on them and need to be cut to length - what does one use to cut these straight?? - BTW, I superglued one of these that I destroyed when I was replacing the cracked tube with a new one from GV - it was my first replacement and I broke the silicon washer at the base - seems to be working fine but that tube will never be removed again - I have cleaned these w/out removing the tube followed by drying time and a dry burn and works pretty well - if these new ones (if they ever come in) don't have a hardier plastic tube I'll order the BDs - Thanks again.