The barrels are optimised to be used with the current generation of kits that provide a separate co-axial MG34 meaning the mantlets already have a hole for the MG barrel, these include the AFV Club Tiger Is and Dragon's Panzer III/IVs, Tiger I/II, Panthers as well as the Sd.Kfz.234/2 Puma.
The newer Dragon Panzer III/IV kits include the hollow MG sleeve as an option with the ABER brass barrel fitting very snugly into the sleeve and you may have to drill though the inner mounting depending on the kit being used.
For both the AFV Club and Dragon Tiger Is it just a simple matter of replacing the kit barrel with the brass barrel as the mantlet hole is the correct size for a good fit, some older Tiger I kits such as those from Italeri or Tamiya may require a 1.3mm hole drilled through the mantlet to take the brass barrel section.
Similarly the new Dragon Puma has a hole already included in the mantlet and you simply add the brass barrel in place of the kit item. The ABER set can also be used to update update sets (no I haven't got the stammers). For this example I have updated the Voyager Models Panzer IV H/J barrel set #VBS0129 by cutting away the resin MG, drilling a 1.3mm hole and adding the brass barrel for improved definition.
The armoscale resin Puma mantlet/metal barrel (set #B35-075) has the mantlet drilled out for the brass barrel to again provide improved definition.
The kits this set can be used on is almost endless with only minor alterations required on older kits which is to cut away the kit MG barrel, drill a hole and add the metal barrel, all quite straightforward really.
Barrels fitted to AFV Club and Dragon Tiger I mantlets
ABER barrel fitted to the Dragon Puma (kit #6256)
and on the armoscale resin mantlet/metal barrel (set #B35-075)
ABER barrel used to update the Voyager Model resin Panzer IV H/J Mantlet (set #VBS0129)
The 5 barrels per set is very good value allowing you update 5 kits from the one set.
Highly recommended