Awesomatix ABH Adjustable Battery Holder set. 
Optional Alloy Battery Holders for A800R. 
Width for battery adjustable via sliding the AM280R in and out.
Length for battery adjustable via P68 Battery adjusters (kit parts). 

Only suitable for A800R.
Total weight: ~6g. 

contains:

2pcs AM280R 

2pcs AM15-R