Internal Halyard Truck 
 
These are available in a variety of finishes.
 
IHT-1 Series: Standard Stainless Steel bearings on a Cast Bearing Race Fits 4" Pole Tops
 
IHT-2 Series: Standard Stainless Steel bearings on a Cast Bearing Race Fits 5" Pole Tops
 
IHT-3 Series: Stainless Steel sealed lubricant bearing assemblies. Fits 7 1/2" Pole Tops
 
xxx appended to the number describes the finish color:
SAT - Satin
ACL - Anodized CLear
ADB - Anodized Medium Bronze (313)
ABL - Anodized Black