Uniseals are used to attach pipe to just about any container in situation where bulkheads will not work. The most common use is on curved surfaces such as storage drums, buckets, and even other pipe.
Feel like rubber, but they are made of Alcryn MPR rated to 40 psi and warranted for 25 years. They are immune to cold, will not harden and hold pressure and vacuum. The sizes correspond to standard Schedule 40 PVC pipe. Fit tank wall thicknesses up to 3/8".