Material: Music Spring Wire (SWP-A)
Weight : 0.7g
Origin: German
Annealed and Rustproofing
Package Contents : 
160% Non-linear performance spring *1pcs 
Features : 
1. Increased bolt cycle speed.
2. The guide rod will not strike the bolt.
3. Improved balance to improve the ‘feel’ which gives a much smoother cyclic action.
4. Reduce recoil.
5. Smooth, consistent BB feeding.