These brushes are what I regularily use for oil painting even though they say acrylic and watercolour. I do not use Oil paint brushes for photo realistic painting, because they are too harsh, the softer brushes are perfect for getting smooth detail.
 
12Pcs Filbert Art Paint Brush Set Nylon Hair Watercolor Acrylic Oil Paint Brush Product Description Features: 100% Brand New. High quality wood material handle and nylon hair