The Anchor Pulley is a lock and release pulley that sets or releases anchor without the need for leaving your seat. Mounting base length is 2-13/16" x 5-1/4", overall length is 7-1/4".
Although the hole in the pivoting part is sized for 1/2" line, it works best with 3/8" line. The smaller line passes through the hole much more easily. Twisted nylon anchor line is a good choice, but you have to customize the anchor pulley to make it work properly.
First of all, disable the spring on the pivoting lock. The anchor pulley works better without it. I cut the leg that goes on the pivoting part and left the coiled part in place to act as a spacer.
Second, if you use 3/8" twisted nylon anchor line, you will need to add a 1/8" - 3/16" shim on top of the serrated part of the base. Otherwise a strong line pull on the anchor end will pull the line through. I hot glued a 1/8" strip of aluminum on top of the serrations and it works great.
I have 5 of these pulleys on my different boats (16' custom and 4 different sized zodiacs). As noted, in the other reviews the springs are not very good, but to be honest they work better without them anyway. After you remove the spring, if you have trouble with the guided catch just cinch down a cable tie (trim it) to the spot where the spring was mounted to remove any "side to side play." Other than that small modification, they have all worked perfectly for 15+ years of solid use. Very sturdy and you can't go wrong for the price.