A.LA pattern p-traps feature a union connection at the top of the u-bend to allow the elbow to swivel, while NY pattern traps are a single body piece without a union swivel connection. They are designed to meet plumbing codes within the two major metropolitan areas of Los Angeles and New York, and are code-compliant in many other areas as well. However, we always advise you check with local authorities regarding plumbing codes in your area before purchasing.