Any product that does not come with your car seat or vehicle is considered an "aftermarket" product. It is never recommended that you use anything extra with your car seat without the express consent of the car seat manufacturer. Here are the reasons that seat-belt tightening devices like the ones shown above are not recommended.

1. A seat that ALREADY meets the federal safety standards "met" the safety standards with the product attached. This says nothing about how this device performs in real life with children climbing in/out of the seat stressing the webbing; repeated use from installing more than once; product being used to "make" an incompatible seat fit, etc.

2. This product does NOT replace a locking clip - if your seat belt requires one, you still have to use one (correctly) in addition to using the product. And if you're using the locking clip correctly...why do you need a product like this?

3. Both products have poor instructions. Both sets of instructions tell the user to:

• install the car seat according to the manufacturer's instructions. Since a car seat installed according to the manufacturer's instructions will be correctly installed, there is no need for either product.
• rock the top of the car seat to check for excess movement. A properly installed car seat may still have movement at the top (especially a rear-facing car seat). The CORRECT way to check for excess movement is AT THE BELT PATH (which neither set of instructions ever suggest)

4. The product can cause damage. According to the manufacturers, the devices did not cause damage during testing.   One set of results obtained from one of the manufacturers showed that in one test, the device did damage the seat belt. However in real life, where overzealous parents can and do over-tighten these devices, damage can happen and has been caused to the car seat and to the seat belts.

5. The packaging can absolve the product manufacturer of liability.

• Some car seat manufacturers warranty will be void if you use a product like this.  For example, Britax specifically forbids the use of such a product with their seats.
• The packaging states that your car seat should be installed according to manufacturer's instructions; most manufacturer's instructions do not include adding a product like this to the seat belt to install the seat.  Doing so may void the warranty of your car seat.
• The packaging specifically states that if you over-tighten the belt, you are responsible.  Any damage to seat belts, car seats, or children is your own fault.
• The packaging specifically states that if you misuse the product (in many cases, simply using the product is misusing the product based on the above statements), any damage to your seat belts, car seats or children is your own fault.

Finally, Kathleen Weber, who was the Director of the Child Passenger Protection Research Program in the University of Michigan Medical School when the testing was done on Mighty-Tite has this to say: "...the product may have limited application but is not appropriate for general use."

So while such a product may have some use for a client who is trying to correctly use their car seat but simply cannot tighten the belt appropriately (because of injury, illness or physical disability), it should not be viewed by the general public as the "required separate tightening tool that will enable everyone to easily and safely secure the child seat without exerting a great deal of effort."

The best tool for correctly installing a child safety seat? A Certified Child Passenger Safety Technician teaching you how.  The cheaper, and definitely safer alternative.