"Bitcoin Unlimited (BU) is a fork from the current Bitcoin protocol that removes the limit of 1MB. The objective of BU is to increase the throughput of Bitcoin transactions. This objective is similar to the one of Bitcoin XT.
Compared to Bitcoin XT, BU does not set any fixed block size, but allows miners to configure the size of the blocks that they create and nodes the size of blocks that they validate. To do so, BU introduces five configurable options in BUIP001, 002, and 005.
1.Maximum Generate Size (MG) is used by miner to specify the size of the block they mine. (Default is set to 1MB.)
2.Excessive Block Size (EB) lets miners and validating node determines the size of block that they accept. If a node sets this option to 1MB, it would reject any block with larger size. Note that this would in effect potentially create a fork in the blockchain, if some node accept blocks of size greater than 1MB while others reject them. (Default is set to 16MB.)
3.Excessive Acceptance Depth (AD) aims at solving the fork issue. Assuming that a node initially rejects a block of size greater than it EB parameter, but that this block is accepted by a majority of miners who mine 'AD' block on top of it, the node will finally accept it.
4.Future Generate Size (FGS) is the maximum size of a block that will be generated in the future (ABH).
5.Proposed Activation Block Height (ABH), the block height at which the new FGS will be put into effect: (ABH – current blockchain height) / 12000 rounded up.