Carrier crystals for use with standard 10.7MHz SSB filters.  These are nominally chosen for the 2.4kHz bandwidth SSB filter that have a centre frequency of precisely 10.700000MHz.  It is usual to set the carrier crystal frequencies to correspond to 20dB down the lower and upper filter passband slopes. 

This can be found with the aid of a precision signal generator and a means of observing or measuring the output signal level from the filter.  Simply calibrate your measuring device at a full signal level and one at 1/10th that level. 

Then apply the signal generator to the filter and monitor its output.  In the centre of the passband should be the full level (less insertion loss).  Then tune to each side of the slope where the level has dropped to 1/10th.  Note these upper and lower frequencies and in your receiver or transceiver, using that filter, set the carrier crystals to those exact frequencies.

It is normal for carrier crystals to be able to be pulled plus or minus 300Hz.

There is also a PCB kit available for a Carrier Crystal Oscillators and Product Detector as a separate item which includes the crystals.  That circuit overcomes the pulling effect normally occurring when trying to use a single oscillator and switched crystals.

Tracked carriage is quite high.  If you use a computer instead of a mobile phone to order then you can click to buy several items up to a value of 50GBP and ask for an invoice.  I then adjust the postage and return to invoice for acceptance and payment.