I mentioned posting this in another thread. Had to dig into few boxes. Here they are. From left to right, House Pipe, Premium 307, Standard 301, Spigot 313. Premium was purchased back in 2018. By that time, the stems were same as Standard acrylic stems. You can see the aluminum chimney in House Pipe, but Premium and Standard just have extension at the end of tenon. Spigot doesn't have chimney at all. But they all function fine as far as dryness is concerned.