EMPIRE BT-4 SPRING KIT
5 Piece Spring Kit For BT-4 Markers, will also fit Tippmann 98/A5/X7 Markers.
Features:
Includes 5 different main/velocity springs, two harder than stock, 1 stock, and 2 softer than stock
Blue Spring - Ultra Light
Green Spring - Light
Black Spring - Stock
Silver Spring - Medium
Red Spring - Hard