@humerafaisal04: hair color developer explained - 10, 20, 30 & 40 vol 🥰👍 : The best use of a hair developer depends strictly on its volume number: use 10 volume for depositing dark color or toning, 20 volume for standard gray coverage and 1-2 levels of lift, 30 volume for 2-3 levels of lift, and 40 volume for maximum lift.📞03006640092 🤩📍Faisalabad