I searched everywhere locally last year for a good quality planter at a decent price.  Local stores had "cheaply" produced planters at a much higher price.  I bought  zip ties to attach them to my railing as suggested.  Because the planters fit so well I won't even need them.  Love the color I choose.  Can't wait to get flowers and veggies growing in them.   Everyone walks by and comments on them, most asking me where I bought them and they are sitting in a stack of three empty.