The K-1A quick disconnect model has an internal locking mechanism. This design requires more handling and machining than an external locking design, but offers weather protected components and additional security from casual thieves who may not be familiar with the push-n-twist locking mechanism. The K-1A can be used with any FireStik antennas up to 5ft (1.5m) long and with all their accessories too. The actual installed size is 2.9" (74mm) high x 0.600" (15mm) diameter. The upper and lower body parts are made of chrome plated machine brass. The locking pin and the spring are made from stainless steel.