I bought 2 and used to use them in mine Honwave 3,8 air-floor.
There are 2 ropes which you can use to secure it into floor but I do recommend to add some ALU or plastic pipe and secure this pipe into tubes safety line.
It will support back of the seat. Seats loose air (very slowly).
So even if you inflate them properly and find that they fit perfectly inside boat and do not need any other mounting part I do recommend to add such pipe.
They are really comfortable but within 1 day you can notice loose od some air.