I don't review things often but when I do it's because I've come across something which I believe is a must-have. We onw a 2018 F3L and my wife and I regularly take 100-300 mile day trips through the Colorado mountains. At 6'4" and 300 pounds, I'm on the large side for certain. My wife is 5'3" and 120 pounds. The seat extension adds 5" but it seems like more. If you ride tandem regularly I strongly recommend this product. We no longer have the hard-stop helmet bump (If you've experienced this you know what I'm talking about). It's worth mentioning we also added the BRP arm rests (shown above in the product images). These two things are ABSOLUTELY worth getting together! My wife's riding experience is much better and far more comfortable for her. She enjoys the extra room and when used with the BRP arm rests her shoulder, elbow, arm, and hand positions are natural and fatigue-free. Bottom line, any time you customize your machine in such a manner that it results in you riding it more often...that's the time and money well spent (why else would you make the investment?)! Be certain to read and understand the instructions first for a frustration-free and easy installation. If, like me, after removing the backrest/trunk, you have to make an adjustment to the factory fastener hole mounting locations, you can do so without any permanent modification to your machine. The whole process took me about 45 minutes...and I took my time and did not rush it. It's a very simple installation. Enjoy!