Plain or Ceramic Coated Heater boxes for Type 1 bugs. Stock style Heater Boxes are 1 3/8 and come Plain or Ceramic Coated. Also available are 1 1/2" Performance Heater Boxes which also come Plain and Ceramic Coated and are Flanged for a better seal to the header. The Flanged Heater Boxes are an Automatic fit to part number 00-7320 and 55-7320 Headers. Sold Each. Click Product Options to choose yours.