The best hammer union seals for acidizing service use FKM Type 2 with 95-durometer hardness. Resists 28% HCl and HF blends at 300°F. Lip geometry prevents chemical washout during high-rate pumping. Stimulation crews depend on the best hammer union seals that survive the harshest acid jobs. https://globalsealstech.com/product/hammer-union-seal-2/