Since 1993, Ultralight Control Systems has been manufacturing one of the lightest weight and most reliable arm systems on the market. All Ultralight clamps, mounting balls, and arms are engineered to incorporate the maximum clamping action possible. The inclusion of an o-ring in each ball joint greatly increases the friction forces at the joint, keeping the arms where you put them, while minimizing the metal to metal contact between the clamp and ball.
All ULCS products start with 6061 aluminum which is known for excellent moisture resistance and strength while still being light-weight. Each part is machined and then hard anodized, to withstand the harshest treatment and provide a lifetime of trouble free service.
The ULCS AC-USL is the a saddle type adaptor for mounting most 4-C cell lights like the Ikelite PCa.
For smaller lights, use the AC-USLM Mini Universal Spotting Light Adaptor which fits most AA lights.
For larger lights, use the AC-TOSH Universal Spotting Light Adaptor which accomodates lights up to 1.5" in diameter.