They pay 20% for the life of your referrals.
According to Alexa rank traffic data, SERPWoo looks to be really popular. They also report having over 18,000 active users.
The SERPWoo SaaS product has 4 tiers of pricing from $49.95/mo to $299.95/mo.
This means you can earn about $9.99 to $59.99/mo for each of your referrals.
They also offer annual billing.