The plastic housings for the XTS line is the same, whether it is a "Ruggedized" ("Immersible" for the 2500) model or not. The difference comes in the chassis. An "R" ("I" for the 2500) chassis has a pressure port and a "Non-R" or "Non-I" does not. Once repairs are made on an R/I model and the radio is back together, you connect a handheld vacuum pump to that port, place a drop of water on the white pads on the vent that is located on the chassis and then pull a vacuum to -6 PSI and wait one minute. If the pressure holds at -6 for one minute, the test is complete and the radio is water tight. If you forget to add the drop of water to the vent, the test will fail. If you did place a drop of water on the vent and the test failed, i.e., the pressure went to -4, then you take off the vacuum pump and put a pressure pump on the port. Next, you pressurize the radio to 6 PSI and dunk the entire radio into a bucket of water and look for bubbles. The bubbles are where the leak is and you should inspect the seals in that area and start over once the seal is replaced. If the test immediately fails, i.e., you can't even get it to go to -6 PSI initially, then there is probably a seal missing or you forgot the drop of water. That vent allows air to flow between the inside and the outside of the radio case, but will not allow water to penetrate, hence why you need to add the drop of water before pulling a vacuum.