Matsal or crab stick is commonly used as kimbap filling. Korean matsal is usually longer than what we're familiar with. Nevertheless, they are just the same. Of course, different brands, different tastes, different prices.
Besides kimbap, you can use this to make tiny pancake side dishes. I like putting this in Japchae too.
This pack has 9 long pieces which I split lengthwise coz it's too thick for kimbap roll.