Do you mean a lob wedge? You have a Pitching Wedge and a Sand Wedge yes?

Anyway, you need to balance your wedges... so you need to find out the loft of your PW and SW and then calculate the difference between the two, then add that to the sandwedge loft to get the right loft for the Lob Wedge.

For example, if you have a 48 degree PW, and a 54 degree SW (6 degree difference) then you'd need a 60 degree lob wedge.

Some people carry 4 wedges, pitching wedge, gap wedge, sand wedge and lob wedge, and these would all have the same loft difference between them too (eg 48, 52, 56 and 60).

Does your set also have an AW?

The callaway site says the X20 has a PW of 45 degrees, and a SW of 55 degrees... but there's an Approach Wedge of 50 degrees (and a Lob Wedge of 60 degrees).

This is the page for the latest X20's. Not sure if you have the latest though.

The spec is further down the page: Callaway x20

As you can see, there's an AW and a LW available... the AW plugs the 10 degree gap between the PW and SW.

Hope you find what you're after. 

Not knowing your game or handicap, you might want to consider the following set up:

Pitching Wedge 48 or 49 degrees

Gap Wedge 52 degrees

Sand Wedge 56 or 58 degrees

This set up gives you a large amount of flexibility in shot making and distance control.

As far as equipment goes I can highly recommend Taylor Made, Cleveland and Ping.

Also, Bobby Jones just came out with a series designed by Jesse Ortiz that is stunning.