This billet idler pulley is specifically designed for severe-duty
applications, such as those running higher boost levels or aftermarket
superchargers like a Whipple or a Kenne-Bell. 
The
pulley is machined to accept twin bearings, which spreads the belt load
over a much larger surface.  The twin bearings provide added
stability and the ability to withstand excessive belt loads. 
The belt surface and back side of the pulley is hard-coat anodized in
black, and a separate bearing dust cover and stainless steel fastener
are included.  These pulleys are as close to bullet-proof as
you will find anywhere.
This
pulley can be installed as a direct replacement for an OEM idler pulley
or anywhere a standard Metco Motorsports idler pulley can be
installed.  
Important
Note:  Metco Motorsports double-bearing idler pulleys are
1.75" wide at the belt surface and are compatible with 10-rib drive
systems, although they can also be used on the 8-rib supercharger
drives of the Mustang Cobra & Lightning truck.  The
picture shown above is of the newest design.