The "weight" of a hair oil typically refers to its viscosity, density, and how it feels when applied to the hair and scalp. It's not about the physical weight in grams or ounces, but rather a subjective description of its thickness, ease of absorption, and the likelihood of leaving a residue. In general, butters are the heaviest oil typed ingredients that you can use. As a rule of thumb, the heaviness of your oil will depend on how it feels in your hand. If it feels very thick and sticky it will likely be heavier than if it feel runny. For example castor oil is very sticky which makes it a heavier oil type than sweet almond oil that is well known to be light. The weight of an oil doesn't necessarily determine its penetration score as jojoba (typical sealant oil) and coconut oil (typical penetrating oil) are both considered as 'medium weight' oil. Overall we recommend focusing on finding an oil that suits your porosity type and then adjust the quantity of that oil depending on your hair's thickness and unique needs. We strongly encourage you to play around with the number of drops you add and also to test different oils to see how different your hair feels with each.