Steller Floors are made of solid hardwood and require a spacer under the baseboards--that's where the gasket comes in.
All solid hardwood floors require an expansion gap around the outside of the room that accommodates any expansion or contraction due to seasonal changes in humidity. Because a Steller Floor is floating, we send a foamed nitrile gasket with every Steller Floor order. This foam is intended to be inserted between your Steller Planks and the wall, under the trim.
Basically, the gasket itself is a spacer. It expands when the floor contracts, and is compressed when the floor expands. Most importantly, it is a gentle reminder to leave a 1/2" expansion gap on either side of 40' wide rooms.
If your room is larger than 40' wide or if you expect changes in RH greater than 10%, please reach out to our team to talk about the expansion gap sizes you might need at email@example.com and 1-800-955-7671.