Rope Stropped Block Kits
Two dimensions define block size:
1) line diameter
2) sheave diameter
So, a 3/4" x 4" block has a sheave 4" in diameter which is grooved for 3/4" line.
Other dimensions of Zephyrwerks blocks are functions of these two primary dimensions.
Blocks can be single or double, single thimble, or thimble top and bottom.