Insanely expensive for an 18 inch long piece of PVC pipe (with a bit of a gasket at one end) but this vendor had a slightly better price in comparison to most others I found.
Saniflo designed it very cleverly so that the seal for the toilet end is internal to the extension. It does install easily and seems to seal completely but it does mean that you can't just substitute a 4" section of thin wall PVC pipe.
The key thing about this is that you can't mount the macerator in or behind the wall without it so if you need one, there's no other option, ya godda buy it.
This item is a perfect fit, thus no leaking, no jimmy work-a-round. It does what it says allows the toilet to be in one roam and the plumbing to be behind the wall out of sight.
This is a great product!!! We purchased the Sani Plus for the lower level bathroom of a Bi-level home. Our plumber installed it to a sink and the toilet. The sink drains great and the toilet flushes excellent, couldn't have made a better choice.