Like many Tunze products, there are some surprisingly and cool features of the "Care Magnet," aquarium magnet cleaner. The care magnet comes in three sizes: Care Magnet Nano Dimensions - 1.77" x 3.07" (45mm x 78mm) Glass Thickness - 1/4" to 3/8" (6mm to 10mm) Includes plastic replacement blade Care Magnet Long Dimensions - 3.38" x 5.51" (86mm x 140mm) Glass Thickness - 3/8" to 1/2" (10mm to 15mm) Includes stainless steel blade and two plastic replacement blades Care Magnet Strong Dimensions - 3.38" x 5.51" (86mm x 140mm) Glass Thickness - 1/2" to .79" (15mm to 20mm) Includes stainless steel blade and two plastic replacement blades - plastic blades are recommended for acrylic tanks The long and strong size has a blue clip on one side that allows you to attach a razor blade allowing you to handle all the hardest to clean areas of your tank. Another nice feature of this magnet is the blade edges which are somewhat raises, making it pretty hard to trap sand which means you won't be scratching your surface. All of the blades are simple to replace and reasonably price, so this cleaner should last you a long time!