Description

While many popular retinol serums come in 30ml bottles, retinol products designed to treat dull skin often feature specialized formulations for brightening and resurfacing. A 120 ml retinol-based product is generally found in larger, multi-benefit body treatments or specialized brand sets (like the 120ml foaming face wash paired with serums). 
Below is a description of typical retinol serum benefits for dull skin and common formulations found in higher volumes:

Description of Retinol Serum for Dull Skin
Targeted Benefits: Specifically formulated to fight dullness, uneven texture, and lack-lustre skin. It accelerates cell turnover, shedding dead skin cells to reveal brighter, more vibrant skin.
Brightening Complex: Often infused with complementary ingredients like Vitamin C, Niacinamide (Vitamin B3), or Hyaluronic Acid to nourish, brighten, and lock in moisture.
Skin Resurfacing: Acts as a powerful anti-aging treatment that softens the look of rough texture, fine lines, and sun spots.
Collagen Boosting: Stimulates collagen production to enhance skin firmness and elasticity, restoring a youthful glow. 

Commonly Recommended Formulations for Dullness
Neutrogena Rapid Tone Repair Retinol + Vitamin C: Focuses on fading dark spots, discoloration, and dullness to reveal an even tone.
Olay Regenerist Retinol 24 Night Serum: Combines retinol with Niacinamide to brighten and smooth, providing hydration without irritation.
CeraVe Resurfacing Retinol Serum: Uses encapsulated retinol to resurface the skin and licorice root extract to brighten, with ceramides to protect the skin barrier. 

How to Use
Use at Night: Retinol makes skin sensitive to sunlight, so it is recommended for evening use.
Start Slow: Beginners should apply 2–3 times per week, gradually increasing to nightly use.
Use Sunscreen: Always apply SPF 30+ the following morning to protect the new skin.