Thumb Turn Interior Side：This Door Lock Cylinder works as a thumb turn cylinder lock with a rotary knob on the inside, letting you lock or unlock without a key, while the anti snap cylinder locks design includes sacrificial grooves that break off under attempted snapping attacks on front doors Anti Snap Protection：Use this Door Lock Cylinder as anti snap cylinder locks with reinforced inner cam, where the lock barrel and keys set includes keys Thumb Lock Exterior：This thumb locks for external doors version of Door Lock Cylinder has a thumb turn on the inside and keyhole outside, letting the door barrel locks with keys operate from both sides Keyed Barrel Set：For door barrel locks with keys, this Door Lock Cylinder comes as a lock barrel and keys set, making the thumb turn cylinder lock suitable for Front/Exterior Doors where one side needs keyless exit during emergencies Snap-On Installation：This snap-on door lock cylinder on the Door Lock Cylinder slides into profile housings, letting the anti snap cylinder locks engage when the cam rotates, Manufacturer: WJIAYAO