It is made of durable materials and finished with a black coating to prevent rust and corrosion. The 4" size refers to the length of the bolt itself, which is the part that extends out from the lock and into the strike plate. This size is suitable for most standard applications and provides a secure locking mechanism that is easy to install and use. The straight tower bolt is designed for a variety of uses, including securing doors and gates. The epoxy black finish gives it a sleek and durable appearance. Fixings and fitting instructions are included for easy installation. The bolt is available in a 4 inch / 100mm size and comes in a black color.