crumb rubber

[Finster]

Hi guys,

Could someone tell me what type/size crumb rubber is used at Indy and other meets and possibly a good source where to buy in the US. With my research it seems it is gauged by mesh size. Also how uniform are the particle sizes? I'd like to get some for use in the garage on rainy days. Plus, I've been thinking of building a screening plant and was wondering if it would be a good idea to use this stuff or not.

Thanks in advance.