This is a Rectangular coil heat exchanger (box shaped coil) used in oil heater. 

 - Material: 304 Stainless Steel (316L, 321, etc. Stainless Steel available to order)
 - Tubing Dimensions (O.D.×Thickness, in./mm): 0.5" × 0.020"/ 12.5mm × 0.5mm
 - Coil Dimensions(Coil O.D x Length x Turns in./mm): 12" x 12" x 4 / 304.8mm x 304.8mm x4