The SP40 will fit a 1.5" (38mm) sling, replacing the SP15

Features:
Fully Bound With Leather - More comfortable on the neck of wearer
5 Section Closed-cell Foam Padding,
Greatly improved shoulder comfort
Improved Non Slip material underneath, helps keep the bag in position
Top Grain Leather used throughout
Billingham Press Studs, it can be moved onto other Billingham products.

The SP40 will fit a 1.5" (38mm) sling, replacing the SP15

Features:
Fully Bound With Leather - More comfortable on the neck of wearer
5 Section Closed-cell Foam Padding,
Greatly improved shoulder comfort
Improved Non Slip material underneath, helps keep the bag in position
Top Grain Leather used throughout
Billingham Press Studs, it can be moved onto other Billingham products.

The SP50 will fit a 2" (50mm) sling, which is in place of an SP20

Features:
Fully Bound With Leather - More comfortable on the neck of wearer
5 Section Closed-cell Foam Padding,
Greatly improved shoulder comfort
Improved Non Slip material underneath, helps keep the bag in position
Top Grain Leather used throughout
Billingham Press Studs, it can be moved onto other Billingham products.

The SP50 will fit a 2" (50mm) sling, which is in place of an SP20

Features:
Fully Bound With Leather - More comfortable on the neck of wearer
5 Section Closed-cell Foam Padding,
Greatly improved shoulder comfort
Improved Non Slip material underneath, helps keep the bag in position
Top Grain Leather used throughout
Billingham Press Studs, it can be moved onto other Billingham products.