IIS Url rewrite rule with request max lenght

Based on this question: IIS Rewrite rule based on length param In windows server 2012 IIS, I would like to create a rule that check for the first parameter only for "n" max digits.

the answer proposed gives me an error,

<match url="product\/([A-Za-z0-9]{4,100}+)\/$" />

throws this error:

The expression contains a repeat expression (one of '', '?', '+', '{' in most contexts) that is not preceded by an expression.

someone else have an idea to resolve? Thank you