Different uses of memory protection schemes have different needs in terms of granularity. For example, heap security can benefit from chunk separation (by using protected "padding" boundaries) and meta-data protection. However, such protection can be done at different granularity(eg. perword, per-block, or per-page), with different performance, cost and memory overhead tradeoffs for different applications. In this paper, we explore these tradeoffs for the purpose of heap security in order to discover whether the "right" granularity exists and how the granularity of protection affects design decisions. We evaluate such tradeoffs based on the current heapsecurity approaches in a single address space operating system.The access control granularities we use are word, 8-byte, 16-byte, 32-byte, and page. We find that none of these schemes is optimal across all applications. In some applications, excessive padding degrades caching performance for coarse-granularity scheme...