Any age, they are allowed at all age levels
Cleats are normally plastic and moulded to the boot sole there are normally 6 to 8 depending on the make of the boot. The normal rugby boot will have aluminium studs which screw in for replacement and these boots carry 6 to 10 studs
6 sole 2 heal. Most forward s use all heal studs (longest allowed) as this allows for geater grip
it can have 6 or more studs
The reason why moulded boots or blades are not allowed in rugby is because they could potentially cause harm to other players and the person who is wearing the boots. Moulded boots don't have the same amount of turn as a normal rugby boot and can cause injuries such as broken ankles and muscle strains which i have experienced myself. Also steel blades could be sharpened not maliciously but could cause cut, this is why referees check studs before kick off. I hope this helps Jack
Alluminium
Soccer boots are lower cut and and 6 studs - rugby boots are cut slightly high at the ankle and can have 8 studs
Rugby boots need studs in order to offer the player grip on grass and mud, which can be slippy.
at astroturf ground
The type of stud is controlled closely by the IRB. On their site there is an excellent explanation of the requirements with sizes and graphics as well. Plus, they have up to date lists of approved equipment allowed. Certainly worth a visit
Now I do not think it is allowed, they have to use plastic studs because once david beckham studded someone in the stomach with metal ones. Ouch! Boots are still made with metal studs so i would say yes, they are.
to gain grip in grass and muddy conditions