These harnesses utilize the available factory female receptacles for attachment points. This is what makes these harnesses so special - they integrate into the airbag system. Many of todays vehicles come with two stage airbag systems that will deploy at different rates depending on whether or not the computer detects that the occupant is buckled in. In a standard 4 point system, there is nothing plugged into the female receptacle, so the computer does not know you are restrained.
In addition, by plugging into the female receptacle, many vehicles (BMW and Mini for example) have a pyrotechnic pre-tensioner built into the receptacle that will automatically tighten the lap belt 2" in an impact. This alone is worth the increase in price over a standard Rallye belt.
Couple the safety benefits with the fact that you can completely remove the harness from the vehicle in less than 10 seconds, you have the best of both worlds: something safe and convenient.
SCHROTH QuickFit restraints are the pinnacle of technology for Street Legal restraints.