My boy played for an hour with these studs on his Canterbury boots - on an artificial surface - and four of them were gone by the sixty minute mark. They seem to tighten okay into the boot, but without any locking grooves in them like the original studs, they loosen with a lot of action. We have to look for another alternative!
we found these studs a great alternative to the 16 & 18mm standard stud. for the youth player, they are perfect on harder ground as the larger studs can make them feel unstable around the ankle.