• Anyone (any hair length, any hair type per the brand) who wants a lightweight, flexible-hold finishing spray rather than a stiff-hold aerosol.
• Useful both as a pre-heat-styling spray (blow-dry, iron, curl) and as a finishing/shine spray after styling.
• Consumer retail product — no professional mixing or salon-only use required, but it's sold through professional/salon-brand channels (Sebastian Professional).
• Not the right pick for someone who needs a strong, all-day, humidity-resistant hold; its hold level is medium/flexible, not maximum.

The main reason to reach for Shine Define over a standard hold-only hairspray is that it's built to do two jobs with one can: a light coat before you blow-dry or use hot tools adds a measure of heat protection, and the same spray finishes a completed style with shine and flexible hold instead of stiffness. That makes it a practical option for anyone who wants fewer products in their routine and prefers movement in their hair over a locked-in, sprayed-stiff look.

• Before heat styling: apply to dry hair in small sections, then blow-dry, flat-iron, or curl as usual.
• As a finishing spray: mist evenly over a completed style from a short distance for shine and flexible hold.
• For more control, apply an additional light layer; brushing through afterward keeps the finish soft rather than stiff.

• Pros: flexible, medium hold that doesn't leave hair stiff or crunchy; doubles as a light heat-styling prep spray so you don't need a separate product before hot tools; satin (not wet-look) finish; can be layered for a bit more control.
• Cons: being alcohol-based, heavy daily use can be drying, especially on color-treated or already-dry hair; the hold level is not strong enough for styles that need to survive humidity or a full day without touch-ups; it's a finishing/styling spray, not a leave-in treatment or deep conditioner.