The elastic heart piece of the 4D PRO REACTION TRAINER 4.0!

NOW WITH IMPROVED RUBBER QUALITY MADE IN GERMANY.

Add or remove Lambdas to fine-tune your 4D PRO Bungee Trainer. You have the choice between regular Lambdas (red) and soft Lambdas (white).

The soft white lambdas are ideal to create the perfect bounce for lighter (90 lbs or less) or added support when used with the regular Lambdas.