10 vol developer cream cannot be used together with permanent dye to improve the hair color level, 10 vol developer contains 3% hydrogen peroxide, if the grade of the target color is lower than or the same as the current hair color, you can use 10 vol oxidant.

20 vol hair developer is used together with permanent dye, it can improve 2-3 levels depending on the hair texture, 20 vol contains 6% hydrogen peroxide, which is the most popular concentration of developer. It can be used to cover gray hair and mix with bleaching powder to brighten hair. Can be mixed with conditioner to get low concentration of developer.

30 vol hair developer is used together with permanent dye, it can improve 3-4 levels depending on the hair texture. 30 vol contains 9% hydrogen peroxide and is suitable for healthy hair. When used with bleach powder, it gives a faster lift than 20 vol but is more difficult to work with.

40 vol hair developer is used together with permanent dye, it can improve 4-5 levels depending on the hair texture. 40 vol contains 12% hydrogen peroxide and is intended for use by professionals only. It is not recommended to use with bleach. If hair needs to be brightened by 4-5 levels, it is recommended to pre-bleach and then use a low concentration of oxidant.