BFM® fitting System Sizing

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The BFM® fitting system comprises spigots and corresponding diameter connectors. Our products are manufactured in standard nominal metric (mm) sizes. 

This helps ensure a consistent fit and also aids in simplifying inventory control. We encourage standardization across equipment wherever possible as this means you will need to keep less variety of spares in stock.

Measuring connectors 600x256


Available Sizes

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  • Diameters
  • Connector Lengths
  • Spigot Length


BFM® fitting spigots and connectors are available in the following diameters:

100mm (4”), 125mm (5”), 150mm (6”) up to 1,650mm (65”)  (in 50mm (2”) increments)

There are some limitations on diameters for certain materials.

Choosing The Right Diameter

It's important to note that the BFM® spigot has a slightly tapered tail as this allows the spigot to be welded onto pipes that may vary slightly in diameter.

Spigot diameters for all sizes over Ø100mm are measured on the inside (ID) at the base of the tail. This means the OD (outside diameter) at the base of the tail is 4mm greater than the ID given 2mm stainless steel.

The OD at the top of the tail is 5mm greater than the base, so a 200mm spigot is 204 OD at the base of the tail and 209 OD at the top where the tail intersects with the lower seat radius.

Connector Lengths

Connector Lengths

Measuring connector Length 400x300The length of the connector is the flexible 'body' of the connector only (measured excluding the snap-band/cuff at each end).

Most of our connectors are available in standard lengths:

  • Minimum of 80mm (3")
  • Increments of 50mm (2") increments from 100mm (4") up to 6 metres (19ft 8")

(Note: for larger diameters from 700mm (27.5") upwards, certain length restrictions apply).


Correct Installation Gap Is Essential

BFM® Installation Gap Icon in Blue
When selecting your connector, it is very important to ensure the initial installation of your spigots have been made according to the correct 'installation gap' (IG).  If the spigots are installed too far apart, or too close together, the connector you choose will not perform at it's best.

Spigot Length

Spigot Length

Spigot Sizing 400x300All standard BFM® spigots are supplied at a standard length of 89mm (3 1/2”), and this comprises a 'head' of 37mm (1 1/2”) (where the two distinctive grooves are) and a 'tail' of 52mm (2").

If space is limited, the tail of the spigot can be trimmed down so that the total length is the minimum of 37mm (1 1/2”) if necessary. However, extreme care needs to be taken to avoid any distortion the spigot when welding as this will have a negative effect on the fit and seal of the BFM® fitting connector.


If you are working in imperial (inches), we have a handy guide to work out at what length to cut the spigot to match an imperial diameter sized pipe.

Lipped Spigot DetailThe BFM® Lipped Spigot has 6mm of the tail 'rolled' outwards, so a Lipped Spigot is 83mm in total length - made up of a head of 37mm  and a 'tail' that is 46mm long 

Connector Limitations

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We have a wide range of materials available in our connector range and they can have different performance, compliance and size availability.

BFM connector group 500 x 240

You can of course refer to each product individually, but to make it easy, we've put together a Quick Reference Limitations Summary which has all the key product information in one easy guide that you can download.

Tips & Guides

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For some useful technical tips and information get you started with selecting the BFM® fitting system.

Connector Comparison

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Helpful information for choosing a BFM® connector, highlighting the key benefits of our blue band connectors in specific applications. 

BFM® connector and spigot installed at Waikato Innovation Centre

Need Help?

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