La Marzocco Complete Sight Glass Assembly Complete water-level sight glass assembly for La Marzocco boilers, including the lens and housing. COMPATIBILITY Fits: La Marzocco boilers INSTALLATION Moderate difficulty - requires boiler access; recommend a technician if you're not comfortable with plumbing work. PRO TIPS While the assembly is out, check the lower return pipe for sediment buildup - a clogged return line is a common cause of sluggish or cloudy sight glass readings.