Recommend using this product with Marui VSR-10 13mm, including replicas. 
The GSI spring guide resolves issues with the original product causing damage to the support and at the same time, the GSI product maximizes strength with a high-performance design. 
It also resolves symptoms of bullet speed degradation by thickening the width of the spring end, which results in better efficiency. 
Tough coloring applied to the surface makes a fast spring response and minimizes surface friction.
Recommend using the right size of spring and piston.
 
•EAN & SKU: 8809899600047, SKU: SG20-MVSRSG13  
•Product Dimension & Weight: 3.68(L)x0.81(W)x0.81(H) inch 1.8 oz
•Package Dimension and Weight:  6.6 (L) x 9.3 (W) x 0.9 (H) inch 2 oz 
• Made in Korea,