Choosing the best clay block for your car depends on several factors, including your detailing experience, the condition of your car's paint, and your specific preferences. Here are a few popular clay blocks that are known for being effective and easy to use:

1. Brilliatech Wash Mitt: This is a popular choice because it combines a wash mitt with embedded clay particles. It's easy to use during regular washing, making it convenient for maintenance detailing.

2. Marflo Speed Clay 2.0: This clay block is designed for quick and efficient use. It's gentle on the paint and effective at removing contaminants without causing marring or scratching.

3. Meguiar's Smooth Surface Clay Kit: Meguiar's offers a complete kit that includes a clay block, Quick Detailer spray, and microfiber towel. This kit is beginner-friendly and provides everything you need for effective paint decontamination.

4. Chemical Guys Clay Block V2: Known for its durability and ease of use, this clay block features a rubber polymer technology that makes it less likely to mar the paint compared to traditional clay bars.

5. Marflo Clay Block: Marflo offers various clay blocks that are well-regarded for their effectiveness and ease of use. They come in different grades suitable for different levels of contamination.

When choosing a clay block, consider the level of contamination on your car's paint, your familiarity with detailing products, and whether you prefer a standalone clay block or one integrated with other detailing tools like wash mitts. Always remember to use a suitable lubricant, such as quick detailer or car shampoo mixed with water, to prevent marring and ensure smooth application.