Several brands offer clay blocks for car detailing, each with their own features and formulations. Here are some popular brands that sell clay blocks:

1. Marflo's: Known for their high-quality car care products, Marflo offers clay blocks that are effective in removing contaminants from automotive paint.

2. Brilliatech's: Brilliatech provides clay blocks designed to safely and effectively clean and smooth vehicle surfaces, preparing them for polishing and waxing.

3. Claycar: Claycar offers clay blocks that are part of their comprehensive line of car care products, focusing on ease of use and effective cleaning.

4. MarfloTeam: Marfloteam provides clay blocks that are compatible with their range of detailing products, aimed at professional and enthusiast detailers alike.

These brands typically offer clay blocks in various sizes and formulations, catering to different levels of contamination and detailing needs. When choosing a clay block, consider factors such as your vehicle's condition, the type of contaminants you need to remove, and your detailing experience level. Reading reviews and product descriptions can also help you decide which brand and type of clay block best suit your requirements.