The product description says the beads are made of a tungsten alloy. According to the listing, tungsten alloy is denser than brass or lead, which helps the beads sink faster for quicker presentation in the water.
Slotted tungsten beads add weight to the fly so it sinks faster, while the slot lets the bead move smoothly on the hook and slide into the hook bend for better positioning during tying.
The available sizes shown in the description include 0.08 inches and 0.10 inches.
Each package contains 70 beads, as stated in the product listing.
The description lists them as suitable for a variety of environments, including rivers, streams, lakes, and ponds.
The slotted opening allows the bead to move smoothly along the hook and to slide into the hook bend; it also lets you secure the bead to the fishing line or tippet through the narrow slot for precise positioning while tying.
The bead is slid into the hook bend via the slot so it can move into position, and the narrow slot lets you thread and secure the bead to the fishing line or tippet for a stable attachment while tying.
The product details indicate these beads are intended for fly fishing.