SEI 205-A20 Mercury 2 Stroke 2.07:1 Replacement Lower unitNote for purchasing:You must verify your Gear Ratio.Call for application assistance if needed, and have your engine serial number ready when calling.The SEI 205 is designed for use with 2 stroke Mercury engines between 70-125 HP from 1987 to present.Specifications:OE Part#: 45-43031A1Spline Count: 13OD of Spline: .873″Length of Spline: 1.440″D/S Measurement: 22 3/8″Gear Ratio: 2.07:1Gear Teeth Count: 14 – 29Item is subject to a 20% restocking fee (Boat Covers, Bimini Tops, Outdrives, Drop Ship Items and Special Order Parts)!**Year, Serial Number, and Horsepower are required to order. Please contact us with this information after you place your order otherwise processing will be delaye