OLAPLEX N°.4 Bond Maintenance™ Strengthening Shampoo

OLAPLEX N°.4 Bond Maintenance™ Strengthening Shampoo extends the brand's bond-care system into a concentrated cleanser. OLAPLEX positions the sulfate-free, color-safe formula to remove buildup while reinforcing vulnerable bonds and improving the appearance of strength, softness, and shine. The standard N°.4 formula is designed primarily for medium-to-coarse textures and all porosity levels.

The strongest use case is damage-prone or chemically treated hair that needs more nourishment than a basic daily shampoo. Independent testing published by Byrdie found that N°.4 cleansed thoroughly and removed dry-shampoo buildup without leaving a squeaky finish. That review also noted that the formula is not the brand's most hydrating option, so dry lengths still benefit from a compatible conditioner.

The verified Amazon listing is the 250 mL / 8.5 fl oz bottle. Its public title identifies this exact Strengthening Shampoo rather than the separate N°.4FINE, N°.4P, or N°.4C formulas. The premium price makes the most sense for shoppers already prioritizing color care, chemical-damage support, or the broader OLAPLEX routine.