This is a cheap but good-value multi-socket adapter and the extra benefit of a USB port. It has a much sturdier plug than many budget adapters, fits securely into my car's 12v socket and doesn't feel as though it's about to fall apart.
The three sockets allow multiple accessories to be used at the same time - eg powering a 12v coolbox (3.5amps), running a sat-nav and charging a phone while the USB port can be used to charge a second phone. Although very versatile, you must note that this is only rated at 5 amps/60W and this is very quickly reached if powering a coolbox: a large coolbox alone can be rated at 60W/5amps and a smaller 24 litre size is usually around 3.5amps/40W so, if you need to run several larger-drain appliances, a higher-rated eg 8amp adapter might be a more suitable purchase. Also the plug is near impossible to prise apart and can't be unscrewed so if the fuse is blown following over-loading then the adapter is written-off.
If you're just looking to run a sat-nav, charge a phone, camera battery or other low-drain items then this will do the job reliably at a low price.