The Lynx 4073 Low Scope Rings For Stud Bases - 30mm, Matte Black is for scopes with 30 mm main tubes, to assist with accuracy. These low scope rings have a stem height of 7 mm.
 
Available in three heights:
Low (7mm from base to scope tube)
Medium (12mm)
High (17mm).
LYNX  1″  SCOPE RINGS FOR  LYNX STUD  BASES:
RG401
4101
1” Low. Black.  Matt
RG411
4102
1” Medium.  Black.  Matt
RG421
4103
1″ High. Black.  Matt
Lynx 30mm  Scope Rings for  Lynx Stud  Bases:
RG471
4073
30mm.  Low.  Black.  Matt
RG476
4072
30mm.  Medium.  Black.  Matt
RG481
4071
30mm.  High.  Black. Matt
Lynx 34mm Scope Rings for Lynx Stud Rings
RG740
3401
34mm Low
RG742
3402
34mm Medium
RG744
3403
34mm High