I've just received this product in double-quick time from Amazon via Royal Mail & must say I'm highly impressed.
It's not precisely a butter knife, as it has a rigid blade rather than the flexible one our recently-deceased butter knife had ( the blade snapped off after flexing for 30 years of married life ), but the term 'spreader' is accurate.
The blade is 3 cm wide at the business end & quite long, and the effect of this is that one judicious scrape with it in a tub of butter or margerine is enough to cover one piece of toast or bread without having to go back to the butter container. Moreover, it also means that one can spread the butter onto the bread/toast with only two movements to effectively cover all the bread slice. Brilliant! It has a similar effect on marmalade.
This saves seconds of your time, but also (Aha!) means your toast stays a bit warmer before reaching your mouth. I hate cold toast.
It occurred to me also that if you run a sandwich catering business, this product would speed up mass-sandwich-production massively. It's easy to control the amount of spread actually going onto the bread, also, probably because of the dimensions & shape of the knife: it's quite big: 22 cm long, half of which is the chunky easy-grip soft rubber handle. Ideal for those with limited grip in their hand, also.
The blade is serrated on one hollowground side & Extremely Sharp, making it easy to cut a pile of toast or sandwiches without tearing, in one action.
Excellent product, robust & very nicely finished in stainless steel. Recommended.