RIDGID 18961 Threading Machine Dies 1 - 2in BSPT. These high-quality dies are designed specifically for RIDGID machine die heads, requiring the British model die head for optimal functionality. Compatible with British Universal die heads including models 504A, 811A, 815A, 816, 817, 856, 911, and 913, these threading dies ensure precise and reliable results every time. Crafted from durable alloy material, these right-hand threading dies are ideal for professional plumbers and contractors looking for efficiency and precision in their work.