I have a hash that has a description of the type of password it is. 
It says "8 lower case alphabetic with the following charsets with the probabilities listed:"

asdfghjkl = .5 probability
ertyuicvbnm = .4 probability
qwzxop = .1 probability.

I understand using a charset, like: -1 asdfghjkl -2 ertyuicvbnm -3 qwzxop 

This leaves me with the question, is there a good way to do this?

?l?l?l?l?l?l?l?l -1 asdfghjkl

Nailed it !
If it's a fast hash I'd just go ahead and do -1 asdfghjklertyuicvbnmqwzxop ?1?1?1?1?1?1?1?1
Thanks, it ended up working. I'm not sure if it was quicker than just running through an 8 character lowercase, but it worked anyway.

One more question, is there a way for a special char/digit replacement within the masking rules?