This adapter will work just fine, if you have two pedals with the jacks at exactly same height, but if not, whenever you will put weight on either pedal, or the pedals' weight itself, could over time damage either the adapted or the input of the pedal.
I only reccomend buying this if you have the option of adjusting the height of individual pedals.
I have fixed this by using some paper which I put under the lower pedals, which works, but isn't pretty nor a permanent solution.
The good side is that it's cheap and replaceable, so if you don't want to spend much and if you don't mind using random things to adjust the heights of your pedals, go for it.