Used correctly, this is a good heating element.
Nice PTC heating element for the price. The one I have will draw as much as 750W at one particular point in it's power curve, but at ideal operating conditions it is 500W. Fuse accordingly, and make sure your temp controller can handle the higher current.
You do need to use these things correctly. There are a number of bad reviews here by folks who apparently don't know what a PTC heating element is.
PTC stands for Positive Temperature Coefficient - the heater will draw less power as it's temperature increases, also known as a self regulating heater.
You must have a fan or blower blowing through the element to get it's rated power. Natural convection is not enough. Without forced airflow, the element will not generate anywhere near it's rated power. Looks like this one requires at least 30cfm of room temp air to get the full 500 watts.
This particular element has an over-temp device attached. If you don't have sufficient airflow, the over-temp device will turn it off. It won't turn back on until it cools down a bit, so no power at all during cool-down.
PTC heaters work well for heating applications that require airflow, like space heaters, dehydrators, or filament dryers (when coupled with a thermostat). They are not the right choice for low airflow applications like ovens or tank heaters, or applications that require temps higher than around 250C/500F. This one is limited to 150c by the over-temp device and plastic end caps.
This is just a heating element, not a complete heating unit. It will require a thermostat, blower, and enclosure at the very minimum. It has exposed electrical wiring, and will get hot enough to cause serious burns or fire if not properly used. Abused sufficiently and it will burn out or burn up. You will need to understand what you are doing to use it safely.