👍SIZE: the 18mm is the diameter of plastic part, the diameter of the felt is 15mm. Please read the size picture carefully before buy. 👍HIGH QUALITY: Our floor protectors are made of stainless steel nail, nontoxic ABS plastic case and soft but thick felt. Strong and long lasting. MULTIFUNCTION: Soft touch felt pads protects hardwood, ceramic tile, linoleum and floors surfaces, prevent from marring and scratches; Slip smoothly, reduces friction vibration & noise while moving furniture. Lengthen the life of the floor. 👍WIDE USE: It is suitable for wooden tables, cedar chests, chairs, curio cabinets, desks, and a variety of other wooden furniture items, It can raise the furniture slightly and protects it from moisture. 👍NO MORE SLIDING OFF: Sometimes adhesive pads or feet cover caps slide off easily, use our floor protectors and say byebye to this trouble. Our floor protectors lasts also far longer than stick-on pads or feet cover caps. And it's easy to replace. 👍INSTALLATION TIP: You'd better pre-drill pilot hole for hardwood to prevent nails from bending,plastic cases from breaking,or furniture feet from cracking damage.