K&N adjustable blue Air Filters come with flange inserts which adjust the filter's flange to one of three inside flange diameters. The flange pod filterflanges are made with ultra-strong molded pliable rubber which absorbs vibration and allows for secure attachment. K&N clamp-on universal air filters are washable and reusable.

Part RG-1001BL Product Specifications
Base Outside Diameter: 6 in (152 mm)
Top Outside Diameter: 4.75 in (121 mm)
Flange Type: Centered
Height: 5.5 in (140 mm)
Filter Material: Cotton Gauze
Top Style: Metal
Top Material/Finish: Chrome
Color: Blue
Weight: 1.7 lb (0.8 kg)

Flanges:
Flange Inside Diameter with no insert is: 4 in (102 mm)
Flange Inside Diameter with adjustable insert is: 3.5 in (89 mm)
Flange Inside Diameter with adjustable insert is: 3 in (76 mm)
Flange Length: 1.125 in (29 mm)


Note:
RG-1001BL Blue Coloured filter - Eventually once it comes time to
wash this filter with K&N Recharge kit 99-5000 or 99-5050, you will find
that the blue colouring will wash out.

K&N currently does not have a blue oil for re making these filters blue.
So when it comes to wash it and re oil it with one of the recharge kits
listed, the red oil (from recharge kit 99-5000/99-5050) will in-fact make
this filter red and it will no longer be blue.