3 ml. I have found that a longer syringe and making sure it is warmed , ie putting the syringe against my body for a few minutes prior, stops the burn. Instead of a 6mm use an 8mm, 31g (5/16ths) u-100 syringe. Be sure you are pinching up. Start with 7 units for 2 weeks, move up to a max of 15 units. Some go for a short time to 22 units but I’ve read it should be a max of 15.