Numbers and units

I have often seen numbers and their units written as one word (without any space or hyphen) e.g. 20ml

Would you write 20flasks or 20 flasks??

The same logic applies to numbers and their units.

Tips

• When the unit is described by the number e.g. 20 ml; add space between the number and the unit.

• When the number and the unit together describe another noun eg. 1-hour incubation; add hyphen between the number and the unit