I also own a 2018 321 RSTS. I didn't like that Jayco didn't include the matching LG hi macs sink covers so I had them made by AIA which is the manufacturer that made my island. AIA is a supplier for Jayco and the RV industry but they also have a residential division and you can get things made for your RV. They already know the exact dimensions for the sink covers of course but they need more than the color though. The color for the 2018 countertop is called Padova but you need to find the serial number for your island. There should be a sticker underneath your cabinet with the info you need. I simply called them up and gave them the serial number and ordered them that way. I have included a picture of mine. They make a huge difference and give you so much more prep space not to mention it looks great.