- Be cautious :(
While this package comes with a metal piston and spring guide, it also comes with a heavier spring. Sure it might up your fps a lot, but only for a few hundred shots. I bet no one knows that the stock spring on the mk96 wears down around a steady 390 fps (with .2s) over a couple hundred shots. Same applies for this spring. A high quality piston alone costs twice as much as this package. This is just another scam to get the noobs to upgrade their rifle so that it has high fps. Let me tell you fps is not everything.
In addition, just because this package comes with a spring guide and piston does not mean your rifle won't break. Ever take into consideration that the trigger box might completely be destroyed after firing a few hundred or maybe fewer shots?
There are other necessary upgrades that are needed to use a heavier spring. Piston, spring guide, cylinder, cylinder head, sears or zero trigger, bolt handle, receiver, etc.
O, and I can prove the fact that the mk96 stock spring wears down quickly. If it did not wear down and shoot a steady 465-500 fps, the internals would not last for more than a few months. So be considered lucky that the spring wears down, otherwise you would have to drop in at least $500 worth of upgrades.
The only reason I gave this a three is because the piston and spring guide will prove more durable than the stock parts. I recommend if you are on a budget and cannot purchase laylax or pdi parts, that you buy this upgrade package and only use the piston and spring guide. Do not use the spring, otherwise your rifle will begin to wear quickly in other places and probably break. Besides this low quality spring will wear down to around the high 300's anyways.
Becoming a serious bolt action player is not cheap nor easy. To get a rifle to shoot like the pros you need serious upgrades and a lot of skill. This package does not provide you with serious upgrades at all.
Take this advice if you plan on staying with the bolt action: Upgrade other internal parts before upgrading the spring. In other words, upgrade for durability and then drop in some kind of high powered spring.