Rings fit neatly around the neck of filtering flasks with side-arm tubing connections. No need to disconnect the tubing and compromise the process. The open ring, made of lead and covered with vinyl coating to protect glassware, is flexible enough to be pulled apart to accommodate a wider vessel. Rings fit neatly around the neck of filtering flasks with side-arm tubing connections. No need to disconnect the tubing and compromise the process. The open ring, made of lead and covered with vinyl coating to protect glassware, is flexible enough to be pulled apart to accommodate a wider vessel.