Traditionally, various types of securitizations have traded in opaque markets. During May 2011 the Financial Industry Regulatory Authority (FINRA) began to collect transaction data from broker-dealers (without any public dissemination) as an initial step towards increasing transparency and enhancing its understanding of these markets. Securitization markets are highly fragmented and require transaction matching methods to construct bid-ask spreads. We study the relationship between bid-ask spreads and transaction characteristics, such as the size of the underlying trade and the path by which trade execution and intermediation occurs. Retail-sized transactions lead to relatively wide spreads because of the absence of competition, while institutionally-sized transactions often result in much tighter spreads. We study the contrast between Registered instruments that are freely tradable and Rule 144a instruments with much more limited disclosures that can only be purchased by sophisticated investors.