The quality of Cloud services is a key determinant of the overall service level a provider offers to its customers. Service Level Agreements (SLAs) are crucial for Cloud customers to ensure that promised levels of services are met, and an important sales instrument and a differentiating factor for providers. Cloud providers offer services at different levels of abstraction, from infrastructure to applications. Also, Cloud providers and services are often selected more dynamically than in traditional IT services, and as a result, SLAs need to be set up and monitoring implemented to match this speed. This paper presents the rSLA language for specifying and enforcing SLAs for Cloud services, allowing for dynamic instrumentation of heterogeneous Cloud services and instantaneous deployment of SLA monitoring. This is predicated on formal representations of SLAs in the language. We describe how the rSLA language and its supporting framework as well as underlying SLA execution model enable the fast deployment of custom SLAs in heterogeneous and hybrid Cloud environments.