Question: what is the best leave in conditioner for extensions?
Answer: Bed Head's Superstar Leave-in Conditioner. It doesn't feel heavy or greasy, it controls frizz and leaves your strands silky smooth. ... 
Joico Daily Care Leave-In Detangler. ... 
Chi Keratin Leave-In Conditioner. ... 
Garnier Fructis Sleek and Shine Intensely Smooth Leave-In Conditioning Cream — Argan Oil and Apricot.