The latest trend in TF or FC is black fuel lines with black anodized fittings.

You see them for blower injector lines, Injector-hat injection lines and more.

These lines are black braided lines with black anodized AN fittings.  Typically these fuel and other lines are stainless steel with red and blue AN fittings.

Can also be used as radiator hose ends instead of aluminum. 

All ferrules are black oxide, which looks like a gun metal except for a stainless steel Size D fitting. 

NOTE: ID sizes are 'tight' measurements and you may want to go up one size if you are at these measurements.        

Here's a photo as a reference.

Sizes are as follows: (here are the aluminum lines, rubber lines and braided lines as referenced below)

SIZE A1 - .024" ID  (compatible braided lines):     .018"
                               (compatible clear lines):  .0157", .0196"
                               (compatible aluminum lines):  .020"                             
                               (compatible rubber lines):      .019", .020"

SIZE A - .029" ID (compatible clear lines):     .028"
                           

SIZE B - .039" ID  (compatible aluminum lines): .031", .035" 
                            (compatible braided lines):     .030"
                            (compatible rubber lines):      .030", .039"

SIZE C - .042" ID  (compatible aluminum lines):   031", 035"
                             (compatible braided lines):      .035"
                             (compatible rubber lines):        .039" 

SIZE D - .051" ID  BLACK OXIDE (darker color)

                           (compatible aluminum lines): .049"
                           (compatible braided lines): .045"
                           (compatible rubber lines): .048", .051"

SIZE D - .051" ID  STAINLESS STEEL (lighter color)
                            (compatible aluminum lines): .049"
                            (compatible braided lines): .045"
                            (compatible rubber lines): .048", .051"

SIZE E - .059" ID  BLACK OXIDE  (darker color)
                            (compatible rubber lines):        .059"
                            (compatible clear lines)           .059"

SIZE E - .059" ID  STAINLESS STEEL (lighter color)

                            ( compatible rubber lines):        .059"
                            (compatible clear lines)           .059"

SIZE F - .063" ID  (compatible aluminum lines):  .063"
                            (compatible braided lines):       .060"
                           

SIZE G - .098" ID (compatible rubber lines): .098"

Each pack contains 8 black ferrules, your choice of size.