The slingshot is the perfect tool for days you want to overload the weight with minimal risk of injury. The band assists you with higher volume reps and weight for max efforts. There are different levels of the slingshot that cost from $50-$65. Its worth the money because it offers a safe method to overloads. They are also easy to use, all you need to do is slide the cuffs up to your elbows and begin your heavy bench presses.
Check out this video from Mark Bell explaining how the slingshot works.
Buy them here: http://www.howmuchyabench.net/sling-shots