This is the Ron Thompson Mini Sinker with Swivel.These mini sinkers come in a small plastic case with several sections for the various different weights.
These mini sinkers have a swivel for your running lead to prevent the lead coming down to your hook length.
The Ron Thompson Mini Sinker with Swivel is also good for preventing tangles on your rigs.
Mini sinkers with swivel
Prevents tangles on your rigs
Prevents lead coming down to hook length
Supplied in plastic case with multiple sections