Which product is typically used for nail strengthening?

Nail hardener is specifically formulated to strengthen the nails, making them less prone to breaking and chipping. It often contains ingredients that help reinforce the natural structure of the nail, and some may also include proteins or other strengthening agents that penetrate the nail plate. This product is particularly beneficial for individuals with weak or brittle nails, providing them with an extra layer of protection and support.

Base coats, while they do provide a foundation for nail polish application and can help with adherence, are not primarily designed for strengthening the nails. Similarly, top coats are meant to seal the polish and add shine, but they do not enhance nail strength. Cuticle oil is used to hydrate and maintain the health of the cuticles and surrounding skin rather than strengthen the nails themselves. Thus, among the options provided, nail hardener stands out as the product specifically aimed at strengthening nails.