There are many different brands, shapes, and sizes of rebar protectors on the market today, and they are all equally effective, providing they meet safety standards requirements. And although they all have different specific functions working with rebar, the common goal is the same. Worker safety.
Examples of varying rebar protector caps can be found on websites and in stores. Mushroom shaped caps are designed for minor or angled contact with rebar. They will not prohibit impalement. Others, more geometrically shaped, have steel reinforcement in them, and are specifically made to protect the worker from being impaled. Some rebar protectors take the wooden cover approach, and are caps equipped with clamps to securely hold a two-by-four. These are ideal when the steel bars are lined in a row, and share the same height. Although each of these rebar protectors are designed slightly different in shape or specific function, they all have the same common goal in mind, to protect people from injury or death. And thanks to OSHA (Occupational Safety and Health Administration) standards, those applied to construction sites have passed adequate safety testing.
Of course the most important and effective of all rebar protectors on the market is the worker him or herself. By not exhibiting proper safety skills at the workplace and during the job, relying instead on a product or device to save them in an emergency, the worker is in higher danger of being injured. But the safer a worker is while working with dangerous materials like rebar steel rods, the more effective rebar protectors become.