Hammershot, Sweet Revenge, and Lawbringer Upgrade Spring (8+ Kg) 8kg custom fitted upgrade spring. Compatible with Nerf Hammershot, Sweet Revenge, and Lawbringer. Mod at your own risk! Increasing the spring tension can break or damage stock internal components of your blaster. Some blasters are extremely hard to reassemble, and we won't be able to troubleshoot problems due to user error. Blaster not included.