General description Specifically designed to attach wood to metal (Max. 4.0mm), the TIMCO Collated Self-Drilling Wing-Tip Steel to Timber Light Section Exterior Silver Screws feature a coarse self-tapping thread with wings that ream out the timber, allowing the screw to achieve maximum R.P.M. without burning out. When the wings hit the metal, they break off to permit a secure fastening. Technical specifications Dimensions: 4.8 x 44 mm Material: Steel Finish: Silver Max. thickness for metal attachment: 4.0 mm