The OK International Bevel Cartridges are compatible with MX 500, MX 5000, MX 5200 and CV 5200, CV 500 Systems and MX RM3E, MX RM6E, MX H1 AV, MX H7 SF CV H1 AV and CV H7 AV solder hand pieces. It has 70 degrees bevel angle. The bevel angle refers to the angle at which the soldering tip is ground, and in this case, its 70 degrees. The 1.78 mm is the length of the tip bevel. For ceramic and high thermal demand application