The 36" ISO Knife, with a 29" cutting surface, is designed for 1/2 lb spray foam removal. They have been designed with an impact resistant handle specially shaped to reduce the risk of the user's hands accidentally sliding forward across the blade in the event of a sudden stop while cutting with it. The replacement blades have an extremely sharp serrated edge. The blades can be sharpened a number of times before needing to be replaced. WARNING - The ISO Knives are extremely sharp. User must use caution; wear protective clothing and good quality heavy duty gloves when handling these tools.