These bolt seat cups are made from stainless steel unlike others which are made from alloy. This means they are stronger and more resistant to wear and tare but also a little heavier than the alloy ones. Suitable for M2 Pan head and Block head bolts.

Personally I use the alloy version of these bolt seat cups on my freestyle frames where I am simply landing on concrete, and I leave them off long range frames where weight is a major consideration. These stainless steel bolt seat cups would be worth the extra weight if you were doing any amount of skidding on concrete.
Many people use these bolt seat cups to simply dress up a frame. However, if you happen to strip a hex recess on a bolt, and you are using bolt seat cups, you will no longer have the option of gripping the bolt head with pliers.

One of my freestyle frames