# Features ## PIN - The Secure Metadata Layer "Pins" can be added to any transaction and broadcast to the network. Pins cannot be changed without changing the input to the signature, which would invalidate the transaction. If the transaction is invalidated by a change to a pin, the block containing the invalid transaction will become invalidated as well, causing a cascading effect invalidating every block chained after it. This feature can be deployed to a variety of file storage, indexing, and retrieval applications. ## Proof-of-Work "FLO" Chain Details Initially, pins were limited to 140 bytes. Currently, 1040 bytes of data can be stored on the blockchain with a maximum block size of 1MB. Currently, 1040 bytes of data can be stored on the blockchain with a maximum block size of 1MB. If the blocks are consistently filled, the maximum block size may be increased. **With a target time of 40 seconds, PIN is fast. In fact, it is 15x faster than Bitcoin, and 3.75x faster than Litecoin.** To further assist with transaction throughput, the maximum ancestor limit for an unspent transaction output (UTXO) chain has been increased from the Bitcoin default of 25 up to 1250. This permits large amounts of information to be efficiently indexed. ## Additional PoW Security for FLO PIN does not allow reorganizations of 100 or more blocks, and uses a continuity of Proof-of-Work blocks to secure the blockchain. Once a transaction receives 100 confirmations (\~1 hour), it cannot be tampered with or removed from the blockchain. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.publicindex.network/about-pin/features.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.