I recently acquired an old firestone style keg, I will be cutting the top off and using it for a HLT on the 3 tier I plan on building soon. Quick ?,What do you guys use for a sight glass? I am considering using a SS compression type fitting and a piece of sight glass tubing from McMaster Carr. I hope to incorporate this into the nipple to the 3/4 shutoff valve I'll be adding to the bottom of the keg. I understand I'll need to be very careful trying to seal the glass in the compression fitting. Any Thoughts? Any ideas on how to mark the glass tube?