There are many different types of pre-emergent granular products on the market, so it is difficult to choose just one that is the best. However, if you are looking for a product that will provide long-lasting results and is effective at preventing weeds from growing, then you should consider using a product containing dichlobenil. This active ingredient is known to be very effective at preventing the growth of both annual and perennial weeds, and it can last for up to 6 months after application. It is important to apply this product before weeds start to germinate in your garden or lawn, so make sure to read the instructions carefully before use.