This spray is aimed at anyone who creates curls or waves with a curling iron or similar hot tool and finds the shape falls out too quickly. KMS lists the hair type as straight to curly and specifically calls it ideal for curl creation in straight hair, which is usually the hardest texture to hold a curl in.

It suits stylists prepping clients for iron sets as well as at-home users comfortable with hot tools. Because it is a medium-hold prep product rather than a strong-hold finishing spray, it fits people who want defined curls that still move.

Curls made with an iron often loosen within hours, particularly on straight, smooth hair. Hot Flex Spray addresses that at the prep stage: its thermopolymer is meant to soften under the heat of the tool and firm up as the curl cools, locking the shape in rather than relying on a heavy hairspray afterwards. If your routine already includes a curling iron and your main complaint is curl longevity, this is the step it is designed to fill.

1. Spray into towel-dried hair.
2. Blow-dry.
3. Shape with hot tools, such as a curling iron, to create the style.

Where it helps:

• Heat-activated polymer is designed to set as hair cools, helping iron curls hold their shape.
• Medium hold keeps curls flexible rather than stiff.
• Applied before blow-drying, so it works into the whole set instead of sitting on top.

Things to know:

• It is designed to work with heat; used alone without hot tools, you lose the main mechanism.
• KMS does not state a heat-protection rating for this spray, so it should not be treated as a dedicated heat protectant.
• Contains a silicone-based polymer (Polysilicone-9), which matters if you avoid silicones.