We don't recommend any Olaplex products be used on clients hair after they have hair extensions in. Olaplex products can be used with other services prior to the extensions being put in the first time (or during move ups/touch up appts), but not after. If the client wants to set an appointment while the hair extensions are in, and want to you to use those products on their own natural hair (just the top section), we recommend they come in and have you expertly section their own hair out and apply the products without them touching the extensions, to avoid any damage to the extensions.