An excellent low cost steel spring from ZCI. These come in a plain plastic bag. 

Features
- The ends of the spring are not flattened unlike some of the more expensive springs.
- Unequal spacing of the coils, called a non-linear or irregular design.
- Zinc coated to protect against rust.
- Length: 170mm, Wire Thickness: 1.3mm

** Please Note: Higher power springs and shorter inner barrel yield lower power, please ensure you have the correct inner barrel to cylinder volume ratio.