ALX Solar Easy solar lighting for ALX Pro railing. Solar post caps to complement our ALX Pro Rail. Inside dimensions measure 4-1/8" x 4-1/8" to fit over post sleeves measuring 4” x 4”. Product Literature Post Cap Care Information - [pdf - 471 KB] - English - French - Spanish Installation Instructions Solar Post Cap Installation - [pdf 102 KB] - English - French FAQ Where can I purchase replacement LED light bulbs? The LED bulbs are part of the whole solar cell component and are not designed to be replaced. The LED bulbs have an average life of 10 years, with a normal usage of 6 to 8 hours per day. We do have Solar Collector Replacement Units available. How long will the rechargeable batteries provided with the solar post cap last? The rechargeable batteries should last approximately one year. Can I use regular, non-rechargeable batteries in the solar post cap light? No, the solar post cap light is designed to be used with rechargeable batteries. If regular batteries are used in the sun, they will destroy the solar collector. We do have Solar Collector Replacement Units available for some post cap lights. SEE ALL FAQ