IU's or international units this is one form of measuring dosage, for example 1 iu = 1/3mg, insulin needles 1/2 inch are international units I have never seen any other type. 2ez is right about the difference in GH on the market there is many different types of mixes out there. here is a example with IE Lilly Humatrope the US brand 15 iu kits in Mexico are 5mg in the US and the French brand are 4iu, IE lilly Mexico does not produce growth they just put there info on the box and insert, 4iu's come from France and the 15iu come from the US. a 1/2 inch insulin needle is fine for the injection of growth, you must be careful when mixing your GH tilt the vial to the side and slowly mix (do not plunge your solution direct into the vial) to use GH correct you must inject around the belly button, 2iu's daily for 5 days in the week, you will do 1 IU at 5:30 am and 1 iu 1 hour prior to bedtime also do not do any carbs 1 hour before and 1 hour after just protein you will find this method works well. (it boils down to basic Math when trying to get you correct dosage)