This part of IEC 60444 describes test fixtures suitable for leadless surface mounted quartz crystal units in enclosures as defined in IEC 61837. These fixtures allow the measurement of (series) resonance frequency, (series) resonance resistance, and equivalent electrical circuit parameters L1, C1 and C0 using the measurement techniques specified in IEC 60444-5 and for the determination of load resonance frequency and load resonance resistance according to IEC 60444-4 and IEC 60444-11. Two test fixtures are described in this document: 1. A fixture using the À-network circuit with electrical values as described in IEC 60444-1 for measurements in transmission mode up to 500 MHz. This fixture includes optional means to add physical load capacitors for the measurement of load resonance parameters up to 30 MHz in accordance with IEC 60444-4. The range of load capacitance is 10 pF or more. Calibration of the measurement system and CL adapter board is explained hereinafter. 2. A fixture based on the reflection method, suitable for a frequency range up to 1 200 MHz. No provisions for adding a physical load capacitance are anticipated. Load resonance parameters can be measured by using the method of IEC 60444-11.