Can you please tell me if these stud are legal for match day?
Those studs look perfectly legal to The Rugby Ref, what makes you think they might not be?
The key question with studs is "are they dangerous". No kinds of blades or studs are banned, as long as they are not sharp or burred (or exceptionally long or wide, see IRB regulation 12).
You may find some useful information on the RFU website here: http://www.rfu.com/TakingPart/PlayerHealth/FAQs
There is a question about blades, where it explains the IRB regulations, explains that they are legal and why.
Please post a comment if you have further questions.
The Rugby Ref