QuickBoost provides you with four 20mm Hispano Mk. II cannon barrels with the smooth barrel fairing removed and replaced with a vented fairing to cover the recoil spring. Please note that there was quite a bit of variety in the exposed barrel of the 20mm Hispano Mk. II cannon depending on what type of wing it was installed in. The Spitfire Mk Vc and Mk Ve wing had different style fairings. The Hurricane, Typhoon, and Mosquito installations and fairings were also quite different.
Of note is the re-sealable packaging that QuickBoost uses that makes the parts easy to review and then stuff back into the package securely. There are no supplied instructions; you simply swap out the kit provided plastic parts with the new QuickBoost replacements. These QuickBoost parts are specific replacements for the kit parts found in the Tamiya series of Spitfire Mk Vb kits. If you have the new Airfix 1/48 Spitfire Mk Vb kit, the QuickBoost QB 48 635 set is designed specifically for it.