Karcher K Series
If your spray wand is like this, general Karcher K adapter fits your pressure washer. All Karcher K2, K3, K4, K5, and K7 fit this model, except K1500, K1600, K1700, K1800, K1900, K2000, K2100, K2200, K2300.
Karcher K1700 and K1800
If you have Karcher K1600, K1700, K1800, K1900, K2000, K2100, K2200, K2300. You need the 1/4" Quick Connection Model.