Dang - there you go - an easy answer... I was all set to explain cutting the 24mg stuff...
Other choice of course is to
buy much higher mg stuff and then cut it (stuff generally costs close to the same, regardless of nic content) to save a couple of bucks.
For example, if you
buy 15ml of the 100mg USA nic being sold by an ECF member, you can cut it with PG or VG (or a combo) to make that 15 ml of 100 mg become 72 ml of 21 mg... just add 57 ml of 0mg liquid.
Hope this helps.
-bogie