I have a sight glass and thermometer on my HLT. I never measure the amount in the mash tun. I don't see any need to, I know what went in. I have a dip stick marked off in gallons for the boil kettle. Since it is low and easy to dip stick measure I don't feel I need the sight glass. I also think it would be more of a PITA to keep clean than the value of having one.