The Trap is a high-quality plaster trap by Keystone. Its top drain valve and all metal construction eliminate the need for costly plumbing, clean-ups and repairs. The compact design of the trap is ideal for all dental lab and dental office sub-sink areas. The built-in viewing window eliminates the guess-work of when to change the liner. The 2.75 gallon liners are available to order in packages of 3 or 6.