Aspire Nautilus X 4ml extension kit to expand your tank in a quick and cost effective way. Expand your Nautilus X with this new 4ML adapter kit. While many people have enjoyed the shorter, low profile Nautilus X with 2ML Pyrex tube, many customers want to upgrade the tank capacity to enjoy this product without the need to refill as often. This Nautilus X Adapter kit is the simple solution. The capacity of your Aspire Nautilus X is increased by replacing the standard pyrex tube with the longer one included in this kit.