is a cmo a pass through security 
a cmo is not a pass through security although they are similar in that they are both securities created from pools of mortgages the bottom linea z tranche is the riskiest tranche in a cmo and the one that takes the longest time to pay out investors will typically consider z tranches if they want to park their money in an investment and not have to worry about adjusting it over time however z tranches are still considered a risk and can be affected by changes in the interest rate environment and if payments are made met on time 