This is a real good choice for the money. Other companies are selling products that are not as good for twice the price. Use as is; Or for remote fill neck applications using hose and clamps.
 This Fits Fuel Cell Tanks with the 4-3/4" bolt pattern. (measure straight across center to center). 
    | Cap Type: | Non Vented Threaded (Custom Threads) | 
  | Specifications: | Color Silver - Anodized Aluminum | 
  | Material: | Aluminum. | 
  | Base Diameter: | 5-1/2" | 
  | Tube Outer Diameter: | 2-1/4" | 
  | Bolt Pattern: | Small 12 Hole = 4-3/4"- Center to Center | 
  | Tube Length Down Center-line: | 4-1/2" | 
  | Gaskets Included: | Yes | 
  | Retainer Ring and Bolts Included: | Yes / 6mm Bolts | 
  | Includes | Cap, Neck, Retainer Ring & 2pc Gaskets, 12pc Nuts | 
  | SEE RELATED ITEMS BELOW! |  |