Comparison : Item # 21N4M-2.75-316, Coned and Threaded Nipples - Pressures to 22,500 psi
Item # 21N4M-3-316, Coned and Threaded Nipples - Pressures to 22,500 psi
Item # 21N6M-3-316, Coned and Threaded Nipples - Pressures to 22,500 psi
Item # 21N4M-4-316, Coned and Threaded Nipples - Pressures to 22,500 psi
Item # 21N6M-4-316, Coned and Threaded Nipples - Pressures to 22,500 psi