Pimp my Miniatures offers two variants of the Rheinmetall rh-120 gun for the Leopard 2A4. There is one with smooth fibreglass fume extractor  and another one with rough texture. There is no indication that they are for a particular kit  so I have tried them with a Hobby Boss Leopard.

The guns come in a long cardboard box containing  a zip bag wrapped in bubble wrap. Inside there is another small zip bag with the mirror of the gun, to avoid losing it as it is a very small piece.

The barrels are 3D printed in one piece (except for the mirror), ready to fit. The print is very good, there are no bands or marks and the barrel is perfectly straight. It comes already clean of supports, which were on the base where you can't see them.

The only problem is that the barrel comes complete, so you have to remove part of the original plastic piece where it is housed. From what I've seen the Italeri and Meng models use the same system and the same part would also have to be cut out.

In the Hobby Boss model the mantlet has the caps and their chains molded on, so you have to be very careful. Once cleaned, the contact area of the barrel is small and the hole is quite large, so for a better fit I added a plastic ring. All this takes quite a bit of work, however assembling the two halves of the original plastic barrel and removing the joint I don't think is any less. Also the Pimp my Minatures barrel has better definition (or is a different type if you use the rough textured one), and it has the flat area underneath that the Hobby Boss one lacks.

Conclusion

A good option to replace the plastic barrel, even if it  requires some work,  removing the seam of the original plastic halves in a barrel with such complex profile is not easy. The result probably saves efforts and time and most important, improves the original.